build: Move lint logic to its own script.

[davecgh]

This is rebased on #3157.

This separates the logic in run_tests.sh that runs all of the linters on all modules in the repository to a separate lint.sh script and updates run_tests.sh to call that script instead. Rather than listing every linter in the script comments, it refers to the .golangci.yml configuration file that specifies them now that it exists.

This allows developers to more easily selectively run only the linters without needing to run all of the tests again.

It also cleans up the comments in run_test.sh to match reality while here.

[jrick]

This allows developers to more easily selectively run only the linters without needing to run all of the tests again.

this works well to only perform linting while skipping testing, but not to perform tests without performing lints.

Having the lint operations in a separate script is fine, but could we change run_tests.sh to take an (optional) parameter to describe which operation to perform, and default to performing all of them?

Another alternative is an "all.sh" script that does all, and break out tests into another script like this PR currently does for linting.

[davecgh]

this works well to only perform linting while skipping testing, but not to perform tests without performing lints.

Having the lint operations in a separate script is fine, but could we change run_tests.sh to take an (optional) parameter to describe which operation to perform, and default to performing all of them?

Another alternative is an "all.sh" script that does all, and break out tests into another script like this PR currently does for linting.

Yeah, that was intentional. The lints are part of the tests. I wasn't worried about having a separate test script, because, unlike the linters, it is pretty trivial to selectively run tests with lints with go test nowadays, including for all modules.

I'm not really opposed to having separate scripts for it, but if we decide to go that route, I'd prefer to do it in a separate PR since this solves the immediate thing it sets out to solve as is.