Let "sort variants alphabetically" assist apply to `match` statements

I have an enum with an increasingly large number of variants that I'd like to sort alphabetically so that they don't get entirely out of hand.

Rust-analyzer already supports doing this for the enum declaration. However, I also have multiple match statements that operate on that enum, and I'd like to sort them in the same order as enum variants.

I can do it with a shell script in simple cases but anything even slightly more complex requires parsing Rust code, so I'd really prefer for rust-analyzer to handle it.

Start by locating rust-analyzer’s existing assist for sorting enum variants and trace how it identifies their order. Then inspect how match statements and complex patterns are represented; done means the assist can sort match arms consistently with the enum declaration without relying on a separate Rust parser.