feat: revisit Bloxroute gRPC client

[mempirate]

📝 Summary

Rebases @efbig's work on removing the async lock from the gRPC client with develop. Configures a couple of small gRPC transport options explicitly.

Bloxroute gRPC repo: https://github.com/bloXroute-Labs/relay-grpc

To Do

• Check if there's any gRPC streams available that we can use. May provide better latency.
  • No streams avail

✅ I have completed the following steps:

• Run make lint
• Run make test
• Added tests (if applicable)

[Copilot]

Pull request overview

This PR refactors the Bloxroute gRPC client to remove an unnecessary async lock (Arc<Mutex<>>), improving performance by leveraging tonic's built-in client cloning capabilities. It also adds explicit gRPC transport configuration for connection keep-alive settings.

• Removes Arc<Mutex<>> wrapper from gRPC client type, using tonic's cheap cloning instead
• Adds explicit gRPC transport configuration for keep-alive behavior
• Simplifies async code by removing lock contention

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/rbuilder/src/mev_boost/bloxroute_grpc.rs	Updates GrpcRelayClient type alias to remove Arc<Mutex<>> wrapper and removes unused import
crates/rbuilder/src/live_builder/config.rs	Removes mutex wrapper from client initialization and adds gRPC keep-alive configuration
crates/rbuilder/src/mev_boost/mod.rs	Changes function signature to take ownership of cloned client and removes async lock operations

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