Add auto script about generating groups and senders for grouping.xml

Auto reflect grouping.xml from annotation.xml to improve auditor script

Bug: b/229287656
Change-Id: I5da68711518d43888c62c530bbe7e90d114c1117
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3609094
Reviewed-by: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Commit-Queue: Baijun Zhu <bjzhu@google.com>
Cr-Commit-Position: refs/heads/main@{#1000182}

tools/traffic_annotation/scripts/README.md

@@ -4,7 +4,10 @@ This file describes the scripts in `tools/traffic_annotation/scripts`.
 # auditor/auditor.py
 
 The new implementation of `traffic_annotation_auditor`. It is meant as a
-drop-in replacement, i.e. you can call it with the same command-line arguments
+drop-in replacement, and it adds new annotations to the grouping xml file.
+After the grouping xml file is generated, we'll decide if the new annotation 
+should be in the report by adding hidden="false".
+i.e. you can call it with the same command-line arguments
 and it should give similar output.
 
 # check_annotations.py