writeString converted every string to []byte before calling
io.Writer.Write, which Go escape analysis reports as escaping to the
heap. io.WriteString uses the io.StringWriter fast path when available
(the standard printer writer is a *bufio.Writer) and falls back to
Write([]byte(txt)) otherwise.
Fixes#2807
Co-authored-by: Pablo Garcia <pablito@MacBook-Neo-de-Pablo.local>
