v1.16: tools: add Google Pub/Sub (backport of #211)

[mergify]

This is an automatic backport of pull request #211 done by Mergify.
Cherry-pick of d8f4f38 has failed:

On branch mergify/bp/v1.16/pr-211
Your branch is up to date with 'origin/v1.16'.

You are currently cherry-picking commit d8f4f38.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   README.md
	new file:   yellowstone-grpc-tools/config-google-pubsub.json
	new file:   yellowstone-grpc-tools/src/bin/grpc-google-pubsub.rs
	modified:   yellowstone-grpc-tools/src/bin/grpc-kafka.rs
	new file:   yellowstone-grpc-tools/src/config.rs
	new file:   yellowstone-grpc-tools/src/google_pubsub/config.rs
	new file:   yellowstone-grpc-tools/src/google_pubsub/mod.rs
	new file:   yellowstone-grpc-tools/src/google_pubsub/prom.rs
	modified:   yellowstone-grpc-tools/src/kafka/config.rs
	modified:   yellowstone-grpc-tools/src/kafka/prom.rs
	modified:   yellowstone-grpc-tools/src/lib.rs
	modified:   yellowstone-grpc-tools/src/prom.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   Cargo.lock
	both modified:   Cargo.toml
	both modified:   yellowstone-grpc-tools/Cargo.toml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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