test(cache): avoid ordering assumptions in testExtended

[joshtrichards]

• Resolves: #

Summary

This test is flaky because it assumes getFolderContents() returns entries in a fixed order, and sometimes it doesn’t.

AFAIK getFolderContents() does not promise insertion order or alphabetical order.

This updates testExtended() to avoid relying on ordering.

Addresses test failures such as this:

There was 1 failure:

1) Test\Files\Cache\Wrapper\CachePermissionsMaskTest::testExtended
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'foo1'
+'foo4'

/home/runner/actions-runner/_work/server/server/tests/lib/Files/Cache/CacheTest.php:804

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[joshtrichards]

/backport to stable34

[joshtrichards]

/backport to stable33