Fix initialization of the faulthandler module

faulthandler requires the importlib if "-X faulthandler" option is present on
the command line, so initialize faulthandler after importlib.

Add also an unit test.

Lib/test/test_faulthandler.py

@@ -7,6 +7,7 @@ import signal
 import subprocess
 import sys
 from test import support, script_helper
+from test.script_helper import assert_python_ok
 import tempfile
 import unittest
 
@@ -256,6 +257,20 @@ faulthandler._read_null()
         finally:
             sys.stderr = orig_stderr
 
+    def test_disabled_by_default(self):
+        # By default, the module should be disabled
+        code = "import faulthandler; print(faulthandler.is_enabled())"
+        rc, stdout, stderr = assert_python_ok("-c", code)
+        stdout = (stdout + stderr).strip()
+        self.assertEqual(stdout, b"False")
+
+    def test_sys_xoptions(self):
+        # Test python -X faulthandler
+        code = "import faulthandler; print(faulthandler.is_enabled())"
+        rc, stdout, stderr = assert_python_ok("-X", "faulthandler", "-c", code)
+        stdout = (stdout + stderr).strip()
+        self.assertEqual(stdout, b"True")
+
     def check_dump_traceback(self, filename):
         """
         Explicitly call dump_traceback() function and check its output.