[TRACKING] v0.15 release

[Mirko-von-Leipzig]

Issues and PRs that should go into v0.15.

• fix(store/state): perform potentially blocking RocksDB access in a blocking context #2076
• Replica should forward write requests to stream source #2089
• feat: rename gRPC submission methods #2094

In addition we of course need the usual release things

• Update to protocol v0.15 once released
• Merge main into next
• Release version bumps