6251: Semantic Highlight: Add Callable modifier for variables r=matklad a=GrayJack
This PR added the `HighlightModifier::Callable` variant and assigned it to variables and parameters that are fn pointers, closures and implements FnOnce trait.
This allows to colorize these variables/parameters when used in call expression.
6310: Rewrite algo::diff to support insertion and deletion r=matklad a=Veykril
This in turn also makes `algo::diff` generate finer diffs(maybe even minimal diffs?) as insertions and deletions aren't always represented as as replacements of parent nodes now.
Required for #6287 to go on.
Co-authored-by: GrayJack <gr41.j4ck@gmail.com>
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>