pytime.h: remove duplicated "#ifndef Py_LIMITED_API"
Issue #22043: Fix _PyTime_gettimeofday() if HAVE_GETTIMEOFDAY

Ensure also that the tv_usec field is consistent: in range [0; 999999].
Issue #22043: time.monotonic() is now always available

threading.Lock.acquire(), threading.RLock.acquire() and socket operations now
use a monotonic clock, instead of the system clock, when a timeout is used.