Set up package scaffolding and CI

[scottmarchant]

Summary

Initial Swift package scaffolding with AsyncEventLoopExecutor foundation and CI wiring. Umbrella: #2.

Details

• de8158c build: Initial commit of swift package init with package name nio-async-runtime and target/library name NIOAsyncRuntime
• 612c87b build: Add dependencies used by NIOAsyncRuntime.
• 73769e2 ci: Set up basic pull request CI using https://github.com/PassiveLogic/swift-dispatch-async/blob/main/.github/workflows/pull_request.yml as a source of inspiration.
• d7f5ff7 feat: Add AsyncEventLoopExecutor that forms the foundation for creating AsyncEventLoop.

Usage Examples

• Spin up an executor and drive scheduled work:

let executor = AsyncEventLoopExecutor(loopID: UUID(), manualTimeMode: true)
executor.enqueue { print("run on loop") }
let jobID = executor.schedule(after: .milliseconds(10), job: { print("delayed") }, failFn: { error in })
await executor.run()
executor.cancelScheduledJob(withID: jobID)

Tests covering the executor and loop behavior: #6.