feat(threading): Add new relay-threading module

[iambriccardo]

This PR a new relay-threading package that provides a thread-based task execution framework for managing concurrent workloads in Relay.

Key Features

• Async Task Pool: Thread-based pool for executing async tasks with configurable concurrency limits
• Builder Pattern: Flexible configuration of thread counts, naming, and panic handling through AsyncPoolBuilder
• Backpressure Control: Bounded task queue prevents resource exhaustion
• Panic Recovery: Built-in handling for both thread and task-level panics
• Tokio Integration: Seamless integration with Tokio runtime for async execution

Example Usage

let pool = AsyncPoolBuilder::new(runtime_handle)
    .num_threads(4)
    .max_concurrency(100)
    .build()
    .unwrap();

// Schedule a task
pool.spawn(async {
    // Task logic here
});

Testing

The package includes comprehensive tests covering:

• Single and multi-threaded execution
• Concurrent task handling
• Panic recovery
• Performance benchmarks for various thread/task