Transfer bazel-gazelle to bazel-contrib

[meteorcloudy]

Description:

This issue proposes transferring the bazel-gazelle repository from the bazelbuild GitHub organization to the bazel-contrib GitHub organization, which is owned by the Community for Bazel project under the Linux Foundation.

GitHub Discussion: https://github.com/orgs/bazelbuild/discussions/2

Impacts:

• GitHub issues & PRs will be transferred to the new repository.
• Branch protection rules will need to be transferred to the new repository.
• Individual maintainers will be transferred to the new repository.
• GitHub teams will NOT be transferred to the new repository and will need to be re-created.
• Bazel CI configurations will need to be updated to point to the new repository.

Read more on Transferring a repository from GitHub documentation.

Checklist:

• [x] Obtain approval from the current project maintainers (@bazelbuild/go-maintainers).
• [x] Obtain approval from the bazel-contrib SIG (@alexeagle).
• [x] Initiate the transfer process on GitHub (@meteorcloudy).
• [x] Update Bazel CI settings and confirm presubmit & postsubmit work (@meteorcloudy).

[alexeagle]

Notes from SIG meeting: this transfer was unanimously approved by a thumbs-up vote.

[fmeum]

I approve for @bazelbuild/go-maintainers

[meteorcloudy]

Transfer is done, Bazel CI has been updated, let me know if there is any problem.