Adjust AsyncTask.THREAD_POOL_EXECUTOR config

Remove the queue, reduce core pool size but no longer let it time out.

Reduce the timeout for additional threads.

If necessary, use a special executor, with an unbounded queue, to run
overflow tasks.

Bug: 123762797
Test: AOSP boots, also with MAXIMUM_POOL_SIZE = 1.
Change-Id: I4bc9593a044d1773ff1878684e2397a7c2a9a87a