gh-115122: Add --bisect option to regrtest (#115123)

* test.bisect_cmd now exit with code 0 on success, and code 1 on
  failure. Before, it was the opposite.
* test.bisect_cmd now runs the test worker process with
  -X faulthandler.
* regrtest RunTests: Add create_python_cmd() and bisect_cmd()
  methods.