Issue: #96529

Right now, the tasks that are done:

• saving the desugaring into an ìmpl_trait_context`.
• add impl_trait_id to rust_ast::AssocConstraint.

In progress:
The next tasks are a break out of what I am trying to accomplish. A bit different from the original tasks in order to be as precise as possible and help with mentoring.

• create visit_assoc_constraint in def_collector and create the local def id there by matching with UniversalInDyn context.
• replace the desugar_to_impl_trait with the associated constraint check.
• remove the enum rust_ast_lowering::ImplTraitContextand add the vector to LoweringContext.
• use that vector in the relevant places and retrieve it through the use of with_hir_id_owner.

Not started yet.

• create a ResolverAstLowering::get_impl_trait_context(LocalDefId) to access the ImplTraitContext value.
• fix method parameter documentation for lower_fn_decl.