Per a comment on #70516 this changes `eq_ignore_ascii_case` to take the generic parameter `S: AsRef<OsStr>` by value instead of by reference.
This is technically a breaking change to an unstable method. I think the only way it would break is if you called this method with an explicit type parameter, ie `my_os_str.eq_ignore_ascii_case::<str>("foo")` becomes `my_os_str.eq_ignore_ascii_case::<&str>("foo")`.
Besides that, I believe it is overall more flexible since it can now take an owned `OsString` for example.
If this change should be made in some other PR (like #80193) then please just close this.
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