perf: use io.WriteString in writeString to avoid heap allocation (#2809)

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>

pkg/yqlib/utils.go

@@ -50,7 +50,7 @@ func readStream(filename string) (io.Reader, error) {
 }
 
 func writeString(writer io.Writer, txt string) error {
-	_, errorWriting := writer.Write([]byte(txt))
+	_, errorWriting := io.WriteString(writer, txt)
 	return errorWriting
 }