[DI] Fixes access of aliases shared services

Fixes #8096 and I noticed that the aliases methods weren't really needed anymore so I removed them. I think it's fine since they were protected, but did it in a separate commit in case you just want the bugfix.

Note that while the DI tests pass, I didn't run this patch as part of a real app. I'd appreciate if someone has the time to verify it still works given it's slightly critical code.