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_sys_settrace.py

@@ -7,7 +7,7 @@ import difflib
 import gc
 from functools import wraps
 import asyncio
-from test.support import import_helper
+from test.support import import_helper, requires_subprocess
 import contextlib
 import os
 import tempfile
@@ -1810,6 +1810,7 @@ class TraceOpcodesTestCase(TraceTestCase):
     def make_tracer():
         return Tracer(trace_opcode_events=True)
 
+    @requires_subprocess()
     def test_trace_opcodes_after_settrace(self):
         """Make sure setting f_trace_opcodes after starting trace works even
         if it's the first time f_trace_opcodes is being set. GH-103615"""