Function basic_text::copy_text_using_status

pub fn copy_text_using_status<R: ReadTextLayered + ?Sized, W: WriteText + Bufferable + ?Sized>(
    reader: &mut R, 
    writer: &mut W
) -> Result<u64>

Like std::io::copy, but for streams that can operate directly on text strings, so we can avoid re-validating them as text.

Also, like copy_text, but uses read_text_substr_with_status to avoid performing an extra read at the end.