Invalid service definition for cache services

Created a merge request.

As mentioned on slack, I'm very confused that this didn't cause any test issues?

Ah, I understand, 2.3.x requires 10.3 and this depends on 📌 Fix MemoryCache discovery and DX Needs review , had not seen that. not sure I really understand that change. Having both the chain and the inner memory bin tagged with cache.bin.memory means that those inner memory bins are actually invalidated twice. And the chain isn't a only a memory bin?

We can choose not to tag the chain as a memory bin, that is an oversight because we used to need that where jsonapi had no proper way of declaring its memory cache backend. As I copied from there, I also copied over the double work.

Given how both inner backends are now properly declared, there is no longer a need for the ChainBackend to be declared as a backend itself.

Yes, not 100% sure about the implications, but I guess that would make sense, but that's a minor performance improvement.

Pushed discussed change to the MR.