Auto merge of #155115 - JonathanBrouwer:rollup-RePrRPQ, r=JonathanBrouwer

Rollup of 6 pull requests

Successful merges:

 - rust-lang/rust#152901 (Introduce a `#[diagnostic::on_unknown]` attribute)
 - rust-lang/rust#155078 (Reject dangling attributes in where clauses)
 - rust-lang/rust#154449 (Invert dependency between `rustc_errors` and `rustc_abi`.)
 - rust-lang/rust#154646 (Add suggestion to `.to_owned()` used on `Cow` when borrowing)
 - rust-lang/rust#154993 (compiletest: pass -Zunstable-options for unpretty and no-codegen paths)
 - rust-lang/rust#155097 (Make `rustc_attr_parsing::SharedContext::emit_lint` take a `MultiSpan` instead of a `Span`)

Author: bors