Revert "block: fix request_queue lifetime handling by making blk_queue_cleanup() properly shutdown"

This reverts commit 22fe1f03e303f0832f227a13a15fc6aa20b2993b.
Revert "block: drop @tsk from attempt_plug_merge() and explain sync rules"

This reverts commit 413af29e52636a23ccd170d7daf13e1131f606ab.