Added support for multiple callbacks for GcsSubscriber

[prithvi081099]

#45445 I have added support for multiple callbacks for GcsSubscriber, but if functionality of failure of a subsequent Subscribe call is needed I can do that as well.

1. While I was adding the support for multiple subscribe. I realized that unsubscribe also needs to be update, but I don't understand how can a subscriber delete his callback to a to publisher with a specific key without deleting all other callback as well.

Why are these changes needed?

Related issue number

Checks

• [x] I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• [x] I've run scripts/format.sh to lint the changes in this PR.
• [ ] I've included any doc changes needed for https://docs.ray.io/en/master/.
  • [ ] I've added any new APIs to the API Reference. For example, if I added a method in Tune, I've added it in doc/source/tune/api/ under the corresponding .rst file.
• [ ] I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • [ ] Unit tests
  • [ ] Release tests
  • [ ] This PR is not tested :(

[anyscalesam]

@rynewang can you take a look?

[rynewang]

@rkooo567 can you take a look?

[prithvi081099]

Hi @anyscalesam, @rkooo567 can you please review this PR?

[dayshah]

Hey what is the use case for this, we currently have no use case for multiple subscriber callbacks.

[github-actions[bot]]

This pull request has been automatically marked as stale because it has not had any activity for 14 days. It will be closed in another 14 days if no further activity occurs. Thank you for your contributions.

You can always ask for help on our discussion forum or Ray's public slack channel.

If you'd like to keep this open, just leave any comment, and the stale label will be removed.

[github-actions[bot]]

This pull request has been automatically closed because there has been no more activity in the 14 days since being marked stale.

Please feel free to reopen or open a new pull request if you'd still like this to be addressed.

Again, you can always ask for help on our discussion forum or Ray's public slack channel.

Thanks again for your contribution!