Implement AST -> HIR generics propagation in delegation

[aerooneqq]

This PR adds support for generics propagation during AST -> HIR lowering and is a part of #118212.

Nearest future work:

• Late-bound lifetimes
• impl Trait params in functions
• Proper propagation of parent generics when generating method call
• Fix diagnostics duplication during lowering of user-specified types
• Support for recursive delegations
• Self types support reuse <u8 as Trait<_>>::foo as generic_arguments2
• Decide what to do with infer args reuse Trait::<_, _>::foo::<_>

r? @petrochenkov

[rustbot]

HIR ty lowering was modified

cc @fmease

[Kivooeo]

would it be possible to split this pr to commits?

[petrochenkov]

would it be possible to split this pr to commits?

@aerooneqq is sitting in the same office with me, we'll figure out how to review this better.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[rust-bors]

☔ The latest upstream changes made this pull request unmergeable. Please resolve the merge conflicts.