[BUGFIX] Fix tests on windows

Some unit tests still have problems on Windows.
- setlocale will not error even if the locale is not found
- file permissions don't work the same as the unix style version
- absolute paths do not start with a slash
- files from finder may contain mixed slashes - generating different hash values when used as key

Tests have either been adjusted to accomodate the differing behaviour or
skipped if appropriate.

Resolves: #88552
Releases: master
Change-Id: I32344c2a0a0797db087a3ccad45d3b626715ab77
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60945


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benjamin Kott <benjamin.kott@outlook.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benjamin Kott <benjamin.kott@outlook.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>