Auto merge of #113690 - aliemjay:opaque-defined-by-trait, r=compiler-errors

allow opaques to be defined by trait queries, again

This basically reverts #112963.

Moreover, all call-sites of `enter_canonical_trait_query` can now define opaque types, see the ui test `defined-by-user-annotation.rs`.

Fixes #113689

r? `@compiler-errors` `@oli-obk`

Author: bors