Merge #8591 #8638

8591: Remove SyntaxRewriter usage in insert_use in favor of mutable syntax trees r=matklad a=Veykril

Unfortunately changing `insert_use` to not use `SyntaxRewriter` creates a lot of changes since so much relies on that. But on the other hand this should be the biggest usage of `SyntaxRewriter` I believe.

8638: Remove SyntaxRewriter::from_fn r=Veykril a=Veykril



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

crates/syntax/src/ast/make.rs

@@ -632,6 +632,7 @@ pub mod tokens {
         SOURCE_FILE
             .tree()
             .syntax()
+            .clone_for_update()
             .descendants_with_tokens()
             .filter_map(|it| it.into_token())
             .find(|it| it.kind() == WHITESPACE && it.text() == "\n\n")