[bazel/infra] Add manual BCR release workflow

[shameekganguly]

Internal tooling

Summary

Adds the publish.yaml workflow to release a tag to the Bazel Central Registry (BCR). This workflow uses the official reusable publish-to-bcr workflow from the bazel team.

For now, the workflow must be triggered manually. Once we have iron'ed out any unforeseen issues over a few releases, we can tie it to our release automation.

The following template files are added to mirror the existing files in the latest manual bcr release for gz-sim.

• .bcr/metadata.template.json
• .bcr/presubmit.yml
• .bcr/source.template.json

Some of the fields are auto-populated by publish-to-bcr based on the repo details when creating a PR in BCR.

Note that MODULE.bazel will be auto-patched by publish-to-bcr to insert the new version based on the tag e.g. tag gz-sim10_10.0.0 --> version 10.0.0. This version will also be added to metadata.json alongside existing versions.

Testing

This PR mirrors the BCR setup for gz-utils: gazebosim/gz-utils#192. See testing instructions there.

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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