fix: process.stdin.pause()

[littledivy]

Attempt 2 at fixing process.stdin pause.

Currently, there is no way to pause ongoing reads. This PR adds op_io_read_stop that races against the blocking read task essentially like a CancelHandle but resets for every read.

I don't think this is the right fix yet, there are still fundamental differences and assumption that read ops are always active and don't pause. This sometimes causes readStop() to prematurely exit as the event loop sees there are no tasks left.

Fixes #26403

[ry]

can you check if this also fixes #28530 ?