Revert "workqueue: fix find_worker_executing_work() brekage from hashtable conversion"

This reverts commit e5dafce9ad7e41dc35feb452c9220e851dfc8085.
Revert "workqueue: use new hashtable implementation"

This reverts commit d2c6fea796cb87f0379531e36fc33b93fca75c17.
Revert "block: queue work on power efficient wq"

This reverts commit 4e74da64cbf020d0b6d86abab73832f0486a3aa4.