Auto merge of #139018 - oli-obk:incremental-trait-impls, r=compiler-errors

Various local trait item iteration cleanups

Adding a trait impl for `Foo` unconditionally affected all queries that are interested in a completely independent trait `Bar`. Perf has no effect on this. We probably don't have a good perf test for this tho.

r? `@compiler-errors`

I am unsure about rust-lang/rust@9d05efb as it doesn't improve anything wrt incremental, because we still do all the checks for valid `Drop` impls, which subsequently will still invoke many queries and basically keep the depgraph the same.

I want to do

https://github.com/rust-lang/rust/blob/9549077a47099dc826039c051b528d1013740e6f/compiler/rustc_middle/src/ty/trait_def.rs#L141

but would leave that to a follow-up PR, this one changes enough things as it is

Author: bors