Support extract variable in macro call

[A4-Tacks]

Implement based first and last token mappings

Example

macro_rules! foo {
    (= $($t:tt)*) => { $($t)* };
}

fn main() {
    let x = foo!(= $02 + 3$0 + 4);
}

Before this PR

Assist not applicable

After this PR

macro_rules! foo {
    (= $($t:tt)*) => { $($t)* };
}

fn main() {
    let $0var_name = 2+3;
    let x = foo!(= var_name + 4);
}