[utils][tests] Adjust timeout-hang.py tolerances (#142089)
The subject test sporadically fails on the AIX builder:
https://lab.llvm.org/buildbot/#/builders/64/builds/3921/steps/6/logs/FAIL__lit___timeout-hang_py
This appears to be an environment issue potentially connected to high
load because the problem is not observed on other AIX machines.
This patch separates the "hard" timeout value from the value used to
signal a hang. This allows for a more generous "hard" timeout value,
which allows observation of cases that take longer to finish despite not
hanging.
