feat: Use GRPC from Swift Package Manager

[AttilaTheFun]

This is a re-do of #1019 which was closed when @brentleyjones 's PR merged, rebased onto the main branch.

This PR updates the GRPC examples to use a version of GRPC from RSPM. This is important because without this change developers would get compiler warnings or errors about duplicate symbols between the GRPC version included with rules_swift and GRPC pulled in through a Swift Package dependency.

I haven't been able to merge this PR previously because, before @brentleyjones merged this fix:
#1385

This is because the swift-atomics package (a dependency of grpc-swift) crashes on ubuntu without this flag.

[cgrindel]

These are moving to https://github.com/cgrindel/swift_gazelle_plugin. Should we apply the changes there and close this PR?

[AttilaTheFun]

@cgrindel so I have already ported these over to swift_gazelle_plugin, but I think having at least one example demonstrating how to use SwiftProtobuf / grpc-swift from RSPM (rather than the one baked into rules_swift) is valuable. It doesn't need to use the gazelle plugin. Once we rip the gazelle plugin out of this repo, we can update the remaining examples to just use the rules_swift_package_manager repository rule + rules_swift directly.

[cgrindel]

OK. Can you run tidy to address the remaining failures?

[AttilaTheFun]

@cgrindel I tried to clean it up, but these tidy checks are failing in CI but not on my local machine:
https://github.com/cgrindel/rules_swift_package_manager/actions/runs/13887594198/job/38854389683?pr=1532
I don't see an actual error message here. It just says that it failed.

I'm on macOS 15 and I see that it's failing on macOS 13 and ubuntu 22.04.