fix: Fix tests unable to fail

[frol]

Resolves #3901.

[frol]

The tests finally pass! The changes are essentially the following:

1. I updated actix to the next beta
2. I introduced near-actix-test-utils (in test-utils/actix-test-utils folder) with two helpers: run_actix_until_stop and run_actix_until_panic (the latter just does not print the stack trace)
3. Replaced all the previous System::builder().stop_on_panic(true) with run_actix_until_stop or run_actix_until_panic (which stops actix System once a panic is caught in any of the actors)
4. I increased some timeouts since given the implementation of run_actix_until_stop, we start hitting the node earlier than we used to do it
5. I also replaced some .unwrap()s with proper handling since we often query the node before the chain is booted up (thus returning us an error that the latest block does not exist)

Overall, the tests were just slightly touched and now we have the CI passing and catching panic correctly.

P.S. To review, you may want to disable white-space changes in the diff