Update gRPC metrics dependency

[adriansmares]

Summary

This PR replaces github.com/grpc-ecosystem/go-grpc-prometheus with github.com/grpc-ecosystem/go-grpc-middleware/providers/prometheus, as the former is deprecated and no longer receives updates.

Changes

• Replace github.com/grpc-ecosystem/go-grpc-prometheus with github.com/grpc-ecosystem/go-grpc-middleware/providers/prometheus.

Testing

Local testing - there are no known metrics changes, but the original repository is no longer maintained.

Regressions

N/A.

Notes for Reviewers

We should upgrade github.com/grpc-ecosystem/go-grpc-middleware to their v2 once they have an official release. The migration guide is already available, and in general the only change that we need to take care of is the depreciation of grpc_ctxtags. The rest of the changes are not affecting us.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.