Remove virtual package requirement laminas/laminas-cache-storage-implementation

[boesing]

Feature Request

Q	A
New Feature	yes
RFC	yes
BC Break	no

Summary

When working on laminas-cache-storage-adapter-benchmark and laminas-cache-storage-adapter-test, having to fulfill the requirement of laminas/laminas-cache-storage-implementation by requiring one of the adapters introduces a bunch of pain.

Whenever there are new major versions to laminas-cache, this becomes a huge pain since first, benchmark and test packages have to support the new major before the adapters itself can get updated and then the actual implementations can bump to the new major (including tests, etc.).

We initially added laminas/laminas-cache-storage-implementation to ensure that there are no projects out there to "upgrade" without having any implementation in-place. With v4, we could now remove this requirement.
Any setup guide is already pointing the users to require the specific cache backend + laminas-cache itself.

I already proposed a change to composer itself to be able to kinda "ignore" virtual packages for non-project packages in composer/composer#11671 but that seems to be against what composer expects how dependency inversion works.
I still think it would be helpful if composer is actually ignoring virtual package requirements in "library" packages but I don't think that this will happen any time soon and thus, I propose to remove laminas/laminas-cache-storage-implementation in v4.0.0.

Any thoughts about this?

[boesing]

Closed with #289