Deconstruct Fiber schedulers and non-blocking I/O introduced in Ruby 3.

Fiber schedulers automate asynchronous execution by intercepting blocking operations (like socket or file I/O) at the interpreter level, turning standard code into non-blocking loops.

Fibers are lightweight concurrency blocks controlled explicitly by the application developer. In Ruby 3, a native Hook Interface was added to the runtime engine. When a Fiber Scheduler is registered (e.g., using gems like Async), any standard blocking invocation—such as sleep, TCPSocket.open, or io.read—automatically hits this scheduler hook. Instead of blocking the entire OS thread, the scheduler yields control of the fiber, schedules it for resumption once the kernel I/O poll completes, and immediately switches execution to another ready fiber.