Fixed ByteStr not padding within its Display trait when no specific alignment is mentioned

[asder8215]

Fixes #152804. Path's Display uses ByteStr's Display, which is where the problem was occurring.

The issue was coming from ByteStr implementation of fmt() in this particular area:

        let Some(align) = f.align() else {
            return fmt_nopad(self, f);
        };
        let nchars: usize = self
            .utf8_chunks()
            .map(|chunk| {
                chunk.valid().chars().count() + if chunk.invalid().is_empty() { 0 } else { 1 }
            })
            .sum();
        let padding = f.width().unwrap_or(0).saturating_sub(nchars);
        let fill = f.fill();
        let (lpad, rpad) = match align {
            fmt::Alignment::Left => (0, padding),
            fmt::Alignment::Right => (padding, 0),
            fmt::Alignment::Center => {
                let half = padding / 2;
                (half, half + padding % 2)
            }
        };

The docs for the align implies that Alignment::Left, Alignment::Right, Alignment::Center comes from :<, :>, and :^ respectively with align() returning None if neither of those symbols are used in the formatted string. However, while padding is taken care of in the aligned cases, we could still have padding for things that don't use alignment like:

assert_eq!(format!("{:10}", Path::new("/foo/bar").display()), "/foo/bar  ");

We shouldn't write to f and return from there when there's no alignment; we should also include any potential padding/filling bytes here.

r? @joboet

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