This PR is required in order to upgrade to the `master` branch version of protobuf. To do this, we upgrade to the latest version of `rules_python` by:
- Adding in explicit dependencies on all PyPi Bazel test dependencies
- Resolving the circular dependency this creates for `xds-protos` by giving it a Bazel build
- Generating the Python code for `xds-protos` as part of `generate-projects.sh` since doing so directly in Bazel would be highly fragily, dependent on many other projects' Bazel builds
Closes#34945
Richard Belleville