git cl format supports formatting certain xml files under tools/metrics.
This CL adds metrics_xml_formatter so that the formatter can be run
with git cl format.
Bug: b/369827156
Change-Id: I5922cd79304aa8e06917aacc9f2d9bd3ed548c2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6072565
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Scott Lee <ddoman@chromium.org>
Scott Lee