Implement `describeKey` for more actions

[fmeum]

[tjgq]

This will only cover ctx.actions.symlink when the output is a declare_symlink. Do you also want to add an implementation for SymlinkAction, which would also cover declare_file and declare_directory outputs?

(Feel free to push back if this isn't something you currently need, I'm happy to import as-is.)

[fmeum]

I added describeKey implementations for more actions.

[fmeum]

@bazel-io fork 7.1.0

[iancha1992]

The changes in this PR have been included in Bazel 7.1.0 RC1. Please test out the release candidate and report any issues as soon as possible. If you're using Bazelisk, you can point to the latest RC by setting USE_BAZEL_VERSION=last_rc. Thanks!