[3.14] gh-152132: Fix bugs in Py_RunMain() (GH-153461) (GH-153466) (#153467)

[3.14] gh-152132: Fix bugs in Py_RunMain() (GH-153461) (GH-153466) (#153467)

[3.15] gh-152132: Fix bugs in Py_RunMain() (GH-153461) (GH-153466)

* Check for signals more often. Previously, a pending exception could
  be removed by PyErr_Clear().
* Only call _PyInterpreterState_SetNotRunningMain() if
  _PyInterpreterState_SetRunningMain() has been called.
* Convert _PyPathConfig_UpdateGlobal() PyStatus error to an
  exception.
(cherry picked from commit cecafebc2e30ab2aac5f046ed5c9fbc75d6bfb51)

Co-authored-by: Victor Stinner <vstinner@python.org>