Rollup merge of #125501 - compiler-errors:opaque-opaque-anon-ct, r=BoxyUwU

Resolve anon const's parent predicates to direct parent instead of opaque's parent

When an anon const is inside of an opaque, #99801 added a hack to resolve the anon const's parent predicates *not* to the opaque's predicates, but to the opaque's *parent's* predicates. This is insufficient when considering nested opaques.

This means that the `predicates_of` an anon const might reference duplicated lifetimes (installed by `compute_bidirectional_outlives_predicates`) when computing known outlives in MIR borrowck, leading to these ICEs:
Fixes #121574
Fixes #118403

~~Instead, we should be using the `OpaqueTypeOrigin` to acquire the owner item (fn/type alias/etc) of the opaque, whose predicates we're fine to mention.~~

~~I think it's a bit sketchy that we're doing this at all, tbh; I think it *should* be fine for the anon const to inherit the predicates of the opaque it's located inside. However, that would also mean that we need to make sure the `generics_of` that anon const line up in the same way.~~

~~None of this is important to solve right now; I just want to fix these ICEs so we can land #125468, which accidentally fixes these issues in a different and unrelated way.~~

edit: We don't need this special case anyways because we install the right parent item in `generics_of` anyways:
https://github.com/rust-lang/rust/blob/213ad10c8f0fc275648552366275dc4e07f97462/compiler/rustc_hir_analysis/src/collect/generics_of.rs#L150

r? `@BoxyUwU`

Author: matthiaskrgr