Inert attributes in `$expr` nonterminals are sometimes duplicated

[petrochenkov]

Reproducer:

macro mac($expr:expr) {
    print_bang!($expr);
}

fn main() {
    mac!(#[allow(warnings)] 0);
}

where print_bang is a proc macro from https://github.com/rust-lang/rust/blob/master/src/test/ui/proc-macro/auxiliary/test-macros.rs

The result looks like this:

PRINT-BANG INPUT (DISPLAY): #[allow(warnings)] 0
PRINT-BANG RE-COLLECTED (DISPLAY): #[allow(warnings)] #[allow(warnings)] 0

The issue can be reproduced after merging #84995, before that PR the example ICEs.

[bvanjoi]

It appears that parse_expr_force_collect has caused duplication of the Expr between the attrs and tokens. Can we remove these duplicated attrs by comparing tokens and attrs?