cache.backend.chainedfast misbehaves when both fast and consistent backends point to the same storage

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Think the issue summary needs an update.

Research why this happens and fix.

What was found and how was it fixed?

The approach in the merge request looks OK to me, but none of the previous attempts at test coverage will be relevant with that approach.

Attached patch against Drupal 10.1.x

@Yogesh Sahu, your patch looks like it's done a PSR-2 reformatting of the entire file, and it's unclear what changes your patch is based on.

Rebased the MR, and added tests for the ChainedFastBackendFactory class.

Seems close to ready just some CI failures in the MR

Hopefully just the quick fix to pass spellcheck

Removing issue summary update as that looks completed in #59

When I ran the tests locally without the fix

testIdenticalService failed with "Symfony\Component\DependencyInjection\ContainerInterface::get('cache.backend.test', 1): object was not expected to be called more than once." = GOOD

testDifferentServices = Passed.

Shouldn't both tests fail?

If I got that wrong then think this is good to be marked RTBC

testDifferentServices() uses the correct way to instantiate the factory, so should pass both before and after.

Committed 9124793 and pushed to 10.1.x. Thanks!