Introduce Fiber::Scheduler#fiber_interrupt.

[ioquatix]

Ruby's IO#close can cause IO#read, IO#write, IO#wait, IO#wait_readable and IO#wait_writable to be interrupted with an IOError (stream closed on another thread).

The fiber scheduler did not implement this for io_read, io_write and io_wait hooks. Finally after several years, someone made a bug report - see socketry/async#368 for background. In order to solve this problem for the fiber scheduler, we need to expose the ability for IO#close to interrupt a fiber.

This PR introduces a new public C function rb_io_interruptable_operation which takes a callback. During that callback, the code may be interrupted. In addition, we expose that as IO#interruptable_operation{...} which does the same. This allows us to implement IO interruption, e.g.

Fiber.schedule do
  io.interruptible_operation do
    # internal read or wait
  end
end

# Will interrupt above fiber:
io.close

See socketry/io-event#130 for the counterpart PR in the io-event gem, e.g. the user code which adopts this feature.

[ioquatix]

Closing in favour of #12839