vm: retire vm_page_lock()
vm_page_lock() and its underlying array of locks, pa_lock[], have been
replaced throughout the virtual memory system by either atomics or
busy-style, per-page synchronization. The Linux KPI support contained
the only remaining use cases. Eliminate or update them as appropriate
to each case.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D50767