Feature: Assist to convert `match` to `let`

struct Example {
    v: i32,
}

fn foo(e: Example) {
    match e {
        Example { v } => undefined(v),
    }
}

This match can be replaced with a let. It would be useful if rust-analyzer would offer to convert it. In this case, rustc does give an applicable suggestion, but that suggestion is only available when check has run and when the program is free of other errors, so it would be useful to have this refactor available even when the program does not compile, for use as an editing tool on the way to getting it to compile.

@rustbot label +A-assists

The issue does not name files or tests. Start by locating rust-analyzer's assist entry points and existing assists for match expressions, then use the provided example as the initial case. Done means the conversion is offered as an editing assist without depending on rustc diagnostics.