feat(grpc,core): Apply shared traffic controller to gRPC API and refactor

[jkrvivian]

Description of change

• Wires the shared TrafficController into the gRPC server as a tower
  Layer, so the same blocklist and tally apply to a given client IP
  regardless of whether it hits the JSON-RPC or gRPC surface.
• Client-IP extraction is factored out of authority_server.rs and reused by the
  new layer.
• Includes follow-up cleanup on the recent traffic-controller port: upstream(core): Port latest traffic controller #11598

Links to any relevant issues

Closes #11668

How the change has been tested

• Basic tests (linting, compilation, formatting, unit/integration tests)
• Patch-specific tests (correctness, functionality coverage)
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes