FEAT Phpunit - update i18n suite for windows / phpunit 10 compatibility

[lekoala]

Description

I tried to run the test suite without warnings on my local machine. Phpunit 9 complains about Phpunit 10 deprecation. I found a nice way around that could be migrated to SapphireTest for other test suites.

I've also made some changes to be able to run this on windows. This should not affect linux/mac os.

Manual testing steps

Run the 18n test suite
See that you get no phpunit 10 deprecation
See that all works well on windows

Issues

#11525 (i'm creating the test for this, and it's easier to work with a test suite that is not making warnings :) )

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