Implement AsyncEventLoop and MultiThreadedEventLoopGroup

[scottmarchant]

Summary

Implements AsyncEventLoop and MultiThreadedEventLoopGroup atop AsyncEventLoopExecutor for non-Posix runtimes. Umbrella: #2.

Details

• 023e473 feat: Implement AsynceEventLoop and MultiThreadedEventLoopGroup using Swift Concurrency and the AsyncEventLoopExecutor. Forms a key foundation for several vapor repositories to use NIO without using NIOPosix. This enables a large amount of wasm compilation for packages that currently consume NIOPosix.

Usage Examples

• Schedule work on a manual-time async event loop and advance time deterministically:

let loop = AsyncEventLoop(manualTimeModeForTesting: true)
let scheduled = loop.scheduleTask(in: .seconds(1)) { "done" }
try await loop.advanceTime(by: .seconds(1))
let value = try await scheduled.futureResult.get()  // "done"

• Run tasks on a MultiThreadedEventLoopGroup:

let group = MultiThreadedEventLoopGroup(numberOfThreads: 2)
let loop = group.next()
let future: EventLoopFuture<String> = loop.submit { "hello" }
let value = try await future.get()
try await group.syncShutdownGracefully()

Corresponding test coverage: #6, #7, #10.