Improve error message when running test passthrough_nodejs_and_python and node or python is not installed.

[rukai]

When running cargo nextest run kafka_int_tests::passthrough_nodejs_and_python, I get the following panic:

thread 'kafka_int_tests::passthrough_nodejs_and_python' panicked at /home/rukai/Projects/Crates/shotover/shotover-proxy/test-helpers/src/lib.rs:48:10:
called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
stack backtrace:
   0: rust_begin_unwind
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/std/src/panicking.rs:662:5
   1: core::panicking::panic_fmt
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/panicking.rs:74:14
   2: core::result::unwrap_failed
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/result.rs:1677:5
   3: unwrap<std::process::ExitStatus, std::io::error::Error>
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/result.rs:1102:23
   4: {async_fn#0}
             at /home/rukai/Projects/Crates/shotover/shotover-proxy/test-helpers/src/lib.rs:42:18
   5: {async_fn#0}
             at /home/rukai/Projects/Crates/shotover/shotover-proxy/test-helpers/src/connection/kafka/node.rs:13:50
   6: {async_block#0}
             at ./tests/kafka_int_tests/mod.rs:49:82
   7: poll<&mut dyn core::future::future::Future<Output=()>>
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/future/future.rs:123:9
   8: poll<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/future/future.rs:123:9
   9: {closure#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:729:57
  10: with_budget<core::task::poll::Poll<()>, tokio::runtime::scheduler::current_thread::{impl#8}::block_on::{closure#0}::{closure#0}::{closure_env#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/coop.rs:107:5
  11: budget<core::task::poll::Poll<()>, tokio::runtime::scheduler::current_thread::{impl#8}::block_on::{closure#0}::{closure#0}::{closure_env#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/coop.rs:73:5
  12: {closure#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:729:25
  13: tokio::runtime::scheduler::current_thread::Context::enter
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:428:19
  14: {closure#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:728:36
  15: tokio::runtime::scheduler::current_thread::CoreGuard::enter::{{closure}}
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:807:68
  16: tokio::runtime::context::scoped::Scoped<T>::set
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context/scoped.rs:40:9
  17: tokio::runtime::context::set_scheduler::{{closure}}
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context.rs:180:26
  18: try_with<tokio::runtime::context::Context, tokio::runtime::context::set_scheduler::{closure_env#0}<(alloc::boxed::Box<tokio::runtime::scheduler::current_thread::Core, alloc::alloc::Global>, core::option::Option<()>), tokio::runtime::scheduler::current_thread::{impl#8}::enter::{closure_env#0}<tokio::runtime::scheduler::current_thread::{impl#8}::block_on::{closure_env#0}<core::pin::Pin<&mut core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>>, core::option::Option<()>>>, (alloc::boxed::Box<tokio::runtime::scheduler::current_thread::Core, alloc::alloc::Global>, core::option::Option<()>)>
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/std/src/thread/local.rs:283:12
  19: std::thread::local::LocalKey<T>::with
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/std/src/thread/local.rs:260:9
  20: tokio::runtime::context::set_scheduler
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context.rs:180:9
  21: tokio::runtime::scheduler::current_thread::CoreGuard::enter
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:807:27
  22: tokio::runtime::scheduler::current_thread::CoreGuard::block_on
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:716:19
  23: {closure#0}<core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:196:28
  24: tokio::runtime::context::runtime::enter_runtime
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/context/runtime.rs:65:16
  25: block_on<core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/scheduler/current_thread/mod.rs:184:9
  26: tokio::runtime::runtime::Runtime::block_on_inner
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/runtime.rs:368:47
  27: block_on<core::pin::Pin<&mut dyn core::future::future::Future<Output=()>>>
             at /home/rukai/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.41.1/src/runtime/runtime.rs:342:13
  28: passthrough_nodejs_and_python
             at ./tests/kafka_int_tests/mod.rs:52:5
  29: lib::kafka_int_tests::passthrough_nodejs_and_python::{{closure}}
             at ./tests/kafka_int_tests/mod.rs:42:41
  30: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/ops/function.rs:250:5
  31: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

The error is not helpful at all "No such file or directory" does not indicate what is going wrong.
This kind of error occurs when attempting to execute a command that does not exist.
In this case "npm" was run but not installed.

We should handle a std::io::ErrorKind::NotFound by panicking with a meaningful error.
It should say something like:

Attempted to run the command `npm install` but npm does not exist, have you installed nodejs?

[zaira-bibi]

I'd be happy to take this up, but would require a little guidance regarding the files that need to be changed.