[3.14] gh-132969: Fix error/hang when shutdown(wait=False) and task exited abnormall...

[3.14] gh-132969:  Fix error/hang when shutdown(wait=False) and task exited abnormally (GH-133222) (GH-135344)

gh-132969:  Fix error/hang when shutdown(wait=False) and task exited abnormally (GH-133222)

When shutdown is called with wait=False, the executor thread keeps running
even after the ProcessPoolExecutor's state is reset. The executor then tries
to replenish the worker processes pool resulting in an error and a potential hang
when it comes across a worker that has died. Fixed the issue by having
_adjust_process_count() return without doing anything if the ProcessPoolExecutor's
state has been reset.

Added unit tests to validate two scenarios:
max_workers < num_tasks (exception)
max_workers > num_tasks (exception + hang)
(cherry picked from commit 598aa7cc98bc1b39f10ec41decddd8dd88799fe1)

Co-authored-by: Ajay Kamdar <140011370+ogbiggles@users.noreply.github.com>