Combines the Windows-hermeticity cluster (#67512 by @webtecnica, earliest;
#71112 by @Sanjays2402; #67196 by @anatolijlaptev1991-ctrl) into one fix:
- scripts/run_tests.sh: env -i forwarded only HOME, but native Windows
CPython resolves Path.home() from USERPROFILE (or HOMEDRIVE+HOMEPATH),
stdlib paths from LOCALAPPDATA/APPDATA, ssl/sockets need SYSTEMROOT,
tempfile needs TEMP/TMP — the strip broke collection tree-wide on
native Windows (issues #67385, #70813). Location vars (never
credentials) are now forwarded, each only when actually set, so
POSIX runs are byte-for-byte unchanged (probe-verified both ways).
PYTHONUTF8=1 added for legacy-codepage consoles printing the
runner's glyphs.
- tests/plugins/memory/test_hindsight_provider.py: _clean_env patched
HOME only; on Windows Path.home() ignores HOME. Now patches
Path.home directly into tmp_path (from #67196).
Not ported: #71112's guard test — it regex-reads run_tests.sh source,
which the test policy bans (never read source code in tests).
Fixes#67385. Fixes#70813.
