Decide whether to replace bazel-skylib

[alexeagle]

Context:

• Rules Authors SIG meeting on 9 July 2024
• Skylib is no longer accepting FRs
• Docs are currently confusing: [FR]: Extend docs to explain difference to other/similar/mirrored functions #885

Now that this repo is under Linux Foundation in bazel-contrib, it's time for a fresh discussion of whether to remove our dependency on bazel-skylib and just fork it the rest of the way.

Why not to fork:

• duplicated effort
• Google's bug fixes in bazel-skylib won't be picked up here, and vice versa

Why to fork:

• when changes aren't accepted to skylib, it will be clear where you could put them instead
• this repo can remove a dependency, which is nice since it's near the root of the Bazel Module graph.