Bump to Mutiny 3.0.0 and Vert.x Mutiny Bindings 3.20.0

[jponge]

This follows the release of Mutiny 3.0.0.

This is a major version bump according to semantic versioning due to the introduction of necessary breaking changes (again, see https://github.com/smallrye/smallrye-mutiny/releases/tag/3.0.0 with the notes on Uni.join().all() and the .onFailure(type) improvements).

Also, this is not to be backported. A 2.9.x branch exists in Mutiny if need be.

[quarkus-bot]

Status for workflow Quarkus CI

This is the status report for running Quarkus CI on commit d63bb6c.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

You can consult the Develocity build scans.

[jponge]

@gsmet @gastaldi This could go in 3.27, but I'm fine with it being in 3.28.