build: Use golangci action and make parallel.

[davecgh]

This updates the GitHub workflow to use the official golangci-lint action which has additional caching logic and also creates GitHub annotations for any issues which makes it easier to identify issues versus needing to dig through build logs.

It also arranges for the linters to run as a separate job which executes in parallel to the go build and tests.

Since the repository has multiple modules and golangci-lint does not support running all modules in the repository directly, this uses a separate job to resolve the modules dynamically and then feeds those into the separate linter job as a matrix of modules (work directories) so the linters run on all modules in the repo.

In order to avoid running the linters as a part of the normal test job while still allowing developers to invoke all of the tests and linters via the "run_tests.sh" script, this separates the linter logic into a separate "lint.sh" script and conditionally invokes that script only when not running as a GitHub action.

Finally, it pins the dependencies for both the action itself as well as the golangci-lint version by using their respective hashes.

[davecgh]

This works as of the latest updates, but it's really not ideal due to the way it has to create multiple jobs that each require independent runners and that it also requires repeating the pinned dependencies which themselves can't be abstracted into variables because GitHub's actions don't support any of the necessary contexts in the uses clause.

Given that, I prefer to wait until golangci-lint can properly lint all modules from a single invocation instead.