Remove unneeded prow plugins/cmds

[upodroid]

Prow has many plugins/cmds that we don't need, or GitHub implemented them as features since we wrote them:

Examples:

• golint, it uses golang.org/x/lint which is deprecated, repositories should be running golangci-lint as a verify/unit test job
• dco. GitHub offers native DCO checking as a repository setting. https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/managing-repository-settings/managing-the-commit-signoff-policy-for-your-repository
• jenkins: We don't use this anymore
• buildifier: We don't use bazel anymore. Also, it's a linter that should run in a verify/lint job

Most of these are pulling large/unmaintained dependencies that we should drop from prow.

[rajibmitra]

I’d like to take a stab at it @upodroid

[upodroid]

Try removing the dco one

[petr-muller]

I agree we should shed this stuff eventually but I'd like to do it in a somewhat controlled way:

1. announce their deprecation and eventual removal (not having a good release process makes this a bit harder 😅) with a specific date in the future
2. make a change in the code first that logs, as a warning, that a Prow instance uses an eventually deprecated plugin
3. only at the date actually remove the functionality, and preferably in a way that does not break a hook instance that still consumes config for the plugin (=fail in checkconfig but do not fail on hook startup)