feat: Implement concurrency-backed NIOThreadPool

[scottmarchant]

Summary

Implements a Swift concurrency-backed NIOThreadPool.

Details

• 2ad8fc4 feat: Implement NIOThreadPool using swift concurrency

Usage Examples

• Start a pool and run work if still active:

let pool = NIOThreadPool(numberOfThreads: 1)
pool.start()
defer { try await pool.shutdownGracefully() }
try await pool.runIfActive {
  // work executed on a pool thread
}

• Submit work bound to an event loop:

let pool = NIOThreadPool(numberOfThreads: 1)
pool.start()
let eventLoop = MultiThreadedEventLoopGroup(numberOfThreads: 1).next()
let future: EventLoopFuture<String> = pool.runIfActive(eventLoop: eventLoop) { "done" }
let result = try await future.get()
try await pool.shutdownGracefully()

Testing Performed

Tests coverage provided in tests ported from NIOPosix: #9.

The changes have also been tested in real-world application by running GraphManager and QuantumProjectManager in the browser to migrate database schemas, connect with our server, and pull data from a real user account.

PR Dependencies

#5

Overview of all changes

All planned changes can be viewed together in #2