Move TRACE calls into WaitOnLock()
LockAcquire is a long and complex function. Pushing more stuff to its
subroutines makes it a little more manageable.
Reviewed-by: Maxim Orlov
Discussion: https://www.postgresql.org/message-id/
7c2090cd-a72a-4e34-afaa-
6dd2ef31440e@iki.fi