Make sure that outer opaques capture inner opaques's lifetimes even with precise capturing syntax

[compiler-errors]

When lowering an opaque, we must capture and duplicate all of the lifetimes in the opaque's bounds to correctly lower the opaque's bounds. We do this even if the lifetime is not captured according to the + use<> precise capturing bound; in that case, we will later reject that captured lifetime. For example, Given an opaque like impl Sized + 'a + use<>, we will still duplicate 'a but later error that it is not mentioned in the use<> bound.

The current heuristic was not properly handling cases like:

//@ edition: 2024
fn foo<'a>() -> impl Trait<Assoc = impl Trait2> + use<> {}

Which forces the outer impl Trait to capture 'a since impl Trait2 implicitly captures 'a due to the new lifetime capture rules for edition 2024. We were only capturing lifetimes syntactically mentioned in the bounds. (Note that this still is an error; we just need to capture 'a so it is handled later in the compiler correctly -- hence the ICE in #131769 where a late-bound lifetime was being referenced outside of its binder).

This PR reworks the way we collect lifetimes to capture and duplicate in AST lowering to fix this.

Fixes #131769

[rustbot]

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