Revert "workqueue: allow more off-queue flag space"

This reverts commit e2455a1a0381c5f2290cafeb5041c7e4ba35212e.
Revert "workqueue: better define synchronization rule around rescuer->pool updates"

This reverts commit a24b578143d4dde1accc73b744ac70352d078292.
Revert "workqueue: change argument of worker_maybe_bind_and_lock() to @pool"

This reverts commit 453adc14ee0f0248c806447d4e08e05dfefeb283.
Revert "workqueue: use %current instead of worker->task in worker_maybe_bind_and_lock()"

This reverts commit 036c4c24ce832d66e007b6f7ecc356bfdd482680.
workqueue: removed unwanted WARN_ON_ONCE