Formatting does not work with match arm having mixed OR clauses and comments

Related to #6060 and #6044. For the below snippet, rustfmt does nothing at all:

enum Foo {
    A,
    B,
    C,
    D,
}

fn main() {
    let foo = Foo::A;
    match foo {
        // Here is a comment
Foo::A |
    // And another one
        Foo::B |
        // Hey look! There's another one
    Foo::C |
// That's a lot of comments
        Foo::D => {}
    }
}

If someone more knowledgeable about rustfmt internals can please confirm that this is a solvable bug, I'd be happy to contribute the fix.

Start with the Rust snippet in the issue and run rustfmt on it to confirm that mixed OR-pattern clauses with comments remain unchanged. Trace the formatting path for match arms and comments, then verify that the example is formatted while preserving its comments and meaning.