Merge #6921

6921: Higher-ranked trait bounds for where clauses r=flodiebold a=Veykril

There is a slight problem with this which is also noted in a FIXME now but `LifetimeParameters` of these ForLifetime where clauses allocate the lifetimes in the corresponding arena as if they were lifetimes of the item itself and not just the clause they belong to. I wasn't entirely sure what I could do about this but given nothing really uses lifetimes like that currently I figured it might be fine? Open to suggestions for that problem.

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>

diff --cc crates/hir/src/code_model.rs
Simple merge

diff --cc crates/ide/src/goto_definition.rs
Simple merge