adjust handling for timers to ensure that no samples follow finalization.
adjust handling for timers to ensure that no samples follow finalization.

block timer signal even for thread-centric timers such as REALTIME
after turning it off. REALTIME was observed to be delivered after it's
timer was turned off.

delete a thread's timer when finalizing a thread to avoid leaking timers.

HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit