add ends_with_ignore_ascii_case str (search) utility

[GlenDC]

It can probably be something like this:

fn ends_with_ignore_ascii_case(path: &str, suffix: &str) -> bool {
    if path.len() < suffix.len() {
        return false;
    }

    let start = path.len() - suffix.len();
    path.get(start..)
        .is_some_and(|tail| tail.eq_ignore_ascii_case(suffix))
}

We already have starts_with_ignore_ascii_case, from which that was ported.
Put it in the same module as that function

Also add sufficient test cases similar to the starts_with version.

[azzamsa]

I’ll submit a fix :)