gh-151626: Fix tests that fail when PYTHONPYCACHEPREFIX is set

[zangjiucheng]

Summary

• Several tests in test_inspect, test_import, test_importlib.test_util,
  test_py_compile, and test_compileall assume the default __pycache__
  bytecode layout and fail when the suite is run with PYTHONPYCACHEPREFIX set.
• Fix: neutralize sys.pycache_prefix (and PYTHONPYCACHEPREFIX for
  subprocess-based tests) where that assumption is made so tests are environment-independent.
• The key pattern for subprocess tests: assert_python_ok() runs with -I
  (isolated mode), which ignores PYTHONPYCACHEPREFIX, so the expected cached
  path must be computed with sys.pycache_prefix=None to match.

• Issue: Some tests fail when __pycache__ prefix is set #151626

[vstinner]

test_inspect fails on Windows. Example:

FAIL: test_details_option_with_aliased_target (test.test_inspect.test_inspect.TestModuleCLI.test_details_option_with_aliased_target)
----------------------------------------------------------------------
Traceback (most recent call last):
File "D:\a\cpython\cpython\Lib\test\test_inspect\test_inspect.py", line 6676, in test_details_option_with_aliased_target
self.assertEqual(output_lines, expected_lines)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Lists differ: ['Tar[116 chars], 'Cached: None', 'Line: 98', ''] != ['Tar[116 chars], 'Cached: __pycache__\\frozencpython-316.pyc', 'Line: 98', '']
First differing element 3:
'Cached: None'
'Cached: __pycache__\\frozencpython-316.pyc'
['Target: ntpath:join (looked up as "os:path.join")',
'Origin: frozen',
'Source: D:\\a\\cpython\\cpython\\Lib\\ntpath.py',
- 'Cached: None',
+ 'Cached: __pycache__\\frozencpython-316.pyc',
'Line: 98',
'']

[zangjiucheng]

I will resolve this today :)

[gpshead]

nice test suite cleanup, thanks!

[miss-islington-app]

Thanks @zangjiucheng for the PR, and @gpshead for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @zangjiucheng and @gpshead, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 564c58c718bc3de9cf3d9bc20cdc06317411c1cd 3.14

[bedevere-app]

GH-152736 is a backport of this pull request to the 3.15 branch.

[miss-islington-app]

Sorry, @zangjiucheng and @gpshead, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 564c58c718bc3de9cf3d9bc20cdc06317411c1cd 3.13

[bedevere-app]

GH-152744 is a backport of this pull request to the 3.14 branch.