cache isCached state for scss resources

[icewind1991]

This saves a significant amount of filecache operations when loading a page.

This extra caching layer is disabled when debug mode is enabled to ensure it doesn't get in the way of development

[skjnldsv]

Code make sense! :)

[MorrisJobke]

Teste and works 👍

[MorrisJobke]

Unit tests fail:

1) Test\Template\SCSSCacherTest::testIsCachedNoFile
TypeError: Argument 2 passed to OC\Template\SCSSCacher::isCached() must be of the type string, object given
/drone/src/github.com/nextcloud/server/lib/private/Template/SCSSCacher.php:181
/drone/src/github.com/nextcloud/server/tests/lib/TestCase.php:210
/drone/src/github.com/nextcloud/server/tests/lib/Template/SCSSCacherTest.php:262
2) Test\Template\SCSSCacherTest::testIsCachedNoDepsFile
TypeError: Argument 2 passed to OC\Template\SCSSCacher::isCached() must be of the type string, object given
/drone/src/github.com/nextcloud/server/lib/private/Template/SCSSCacher.php:181
/drone/src/github.com/nextcloud/server/tests/lib/TestCase.php:210
/drone/src/github.com/nextcloud/server/tests/lib/Template/SCSSCacherTest.php:283

[MorrisJobke]

Let me check if I can fix the tests.

[MorrisJobke]

Let me check if I can fix the tests.

Fixed them. They worked locally. Let's wait for CI then.