Release workflow improvements

[nirinchev]

There are several non-critical improvements that we've identified with the release workflow. I'm listing all of them in the same issue, but we can pull them out as we start working on it.

1. Move publish cocoapods job to macos-14. It's taking a lot of time to build everything on the x64 intel runners.
2. Add retries to test-installation step. It may take a few minutes between a pod being published and it getting indexed, so the workflow will sometimes fail just because it's not finding the pod immediately after publishing (https://github.com/realm/realm-swift/actions/runs/8727746319/job/23948821401).
3. Change the publish workflow so that it runs on the release PR and merge it at the end rather than have it run on top of master.

[sync-by-unito]

➤ PM Bot commented:

Jira ticket: RCOCOA-2336