[TASK] Move NoopPasswordHash fixture to MFA tests

The NoopPasswordHash fixture is currently used in MFA provider tests
only. To declutter the Tests/ directory, the fixture directory is now
moved to core/Tests/Unit/Authentication/Mfa/Provider/.

Resolves: #97920
Releases: main, 11.5
Change-Id: I86544bf897a26a2565278e2432831adde7154be8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75136


Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>