Different highlighting scopes for entity definitions vs. uses

[TheOnlyMrCat]

I'm making a minimal colour theme for myself based on Tonsky's Alabaster theme, and have run into a problem.

Alabaster highlights function/variable/type definitions, but not usages. Helix's highlight queries don't differentiate between the two cases. For example, in this short Rust snippet:

fn recursive() {
	recursive()
}

both instances of recursive receive the same highlighting scope (function), where I'd like to highlight them differently.

This looks like it'd require changes to all the queries to add something like: @function.definition, @function.definition.macro, (or some kind of scope with definition in it), as well as changes to all the themes to add highlights for them (since for the most part they won't be able to substring match anymore)

I'm happy to make a PR to update the queries and themes to make this change, if this is something the project wants?

Related: #14786