[GH-8471] undeprecate partials completly

[beberlei]

This undeprecates SELECT PARTIAL DQL queries. EntityManager::getPartialReference is still deprecated, since it will be indistinguishable from EntityManager::getReference in the future.

Related:

• Deprecate Partial Objects #8471
• Reintroduce PARTIAL, but only for non-object hydration. #11365
• Remove partial syntax in DQL #10985

[kevinpapst]

Probably not the best place, but I don't know where else:

This actually takes away a huge burden. I already invested many hours in replacing PARTIAL with the new fetchMode() but many use-cases were not covered and I wonder (and hope) that those are still on the roadmap ... but removing these specific deprecation actually improves my DX a lot.

Thank you 👍