gh-114099: Add test exclusions to support running the test suite on iOS (#114889)

Add test annotations required to run the test suite on iOS (PEP 730).

The majority of the change involve annotating tests that use subprocess,
but are skipped on Emscripten/WASI for other reasons, and including
iOS/tvOS/watchOS under the same umbrella as macOS/darwin checks.

`is_apple` and `is_apple_mobile` test helpers have been added to
identify *any* Apple platform, and "any Apple platform except macOS",
respectively.

Lib/test/test_code_module.py

@@ -160,6 +160,7 @@ class TestInteractiveConsoleLocalExit(unittest.TestCase, MockSys):
         self.console = code.InteractiveConsole(local_exit=True)
         self.mock_sys()
 
+    @unittest.skipIf(sys.flags.no_site, "exit() isn't defined unless there's a site module")
     def test_exit(self):
         # default exit message
         self.infunc.side_effect = ["exit()"]