Allow pausing Watchdog on the current thread

Since we start the watchdog early during boot, we may have some false
positives where the watchdog thinks a thread is blocked but it
is just running a long task. This cl enables us pause the watchdog
triggering for the current thread and resume the triggering after
the long running task. An alternative would be pausing for a specified
duration without an explicit resume but that may be difficult
to find an upper bound for tasks across all devices.

For now the primary long running task is dexopting which happens on
the main thread during boot. We pause the watchdog triggering on the
main thread and resume afterwards.

Test: Verified with logs that pausing the Watchdog pauses triggering
and resuming resumes triggering
Bug: 132076426

Change-Id: I3876c41e6d0e41d044a5b1d5e57f894c7fb4fb0e