**What type of PR is this?**

Documentation

**What package or component does this PR mostly affect?**

go_deps

**What does this PR do? Why is it needed?**

Document the `go_deps` extension.

Also remove some ancient and unsupported repo rules from the docs.

**Which issues(s) does this PR fix?**

Fixes #

**Other notes for review**

---------

Co-authored-by: Jay Conrod <[email protected]>

Also clean up `.bazelrc` and presubmit configs.

Fixes #2012

**What type of PR is this?**
Bug fix

**What package or component does this PR mostly affect?**
merger

**What does this PR do? Why is it needed?**
I found that used idents in assignment expression rhs position have
their load statements removed. This PR adds those idents to used symbols
collection in `FixLoads` fn.

Drops a stray `continue` that could result in incorrect Go module
versions being reported if they are declared by a module further down in
the tree than one that declares a `bazel_dep`.

Warnings now look like this:
```
Mismatch between versions requested for Go module github.com/cloudflare/circl:

  bazel_dep version (MODULE.bazel): 1.3.7 (as "circl")
  Go module version (go.mod):       1.3.8

Either ensure that you have

  bazel_dep(module_name = "circl", version = "1.3.8")

in your MODULE.bazel file or downgrade the Go module version via

  bazel run @my_rules_go//go:go -- get github.com/cloudflare/[email protected]

...
The following Go modules were required by the root module at the given versions, but were implicitly updated to higher versions due to transitive dependencies:

  github.com/stretchr/testify: v1.6.1 -> v1.8.0
  github.com/bazelbuild/buildtools: v0.0.0-20230317132445-9c3c1fc0106e -> v0.0.0-20240918101019-be1c24cc9a44
  github.com/bazelbuild/rules_go: v0.39.1 -> v0.50.1
  golang.org/x/sys: v0.15.0 -> v0.25.0

Update the root module's dependencies to match the resolved versions via:

  bazel run @my_rules_go//go:go -- get github.com/stretchr/[email protected] github.com/bazelbuild/[email protected] github.com/bazelbuild/[email protected] golang.org/x/[email protected]

```

There are some small changes to fix update:
- remove some legacy code that we don't need anymore
- error handling simplification
- unnecessary loops

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**What type of PR is this?**

> Uncomment one line below and remove others.
> Bug fix

**What package or component does this PR mostly affect?**

> For example:
> all

**What does this PR do? Why is it needed?**
The label format changed with Bazel 8 and needs to be adapted here

**Which issues(s) does this PR fix?**

Fixes #2019

**Other notes for review**