ANDROID: improve trusty kthread priority

Add 'signaled' flag that can be used by nop_work_func()
on each processor to boost priority only when necessary.

Slight rework to calculating the correct priority for kthread
based on several factors. Add trace point for dequeue.

Bug: 260619596
Change-Id: If0ae0f22132a41157b62a0f51f510aa05f141c63
Signed-off-by: Brandon Anderson <brandonand@google.com>