[WIP] Add ide-assist: fix_closure_body

[A4-Tacks]

Problems

• Cannot obtain target type when closure parameters do not match
  - ctx.sema.expr_adjustments(expr): is empty vec
  - ctx.sema.type_of_expr(expr)?.adjusted(): is empty parameters (input closure-expr)

Reference #20775

Example

fn foo() -> impl Fn(i32) {
    ||$0
}

->

fn foo() -> impl Fn(i32) {
    |it| {$0}
}

[ChayimFriedman2]

See #8676 for why this is hard.