Add missing descriptors to Perfetto difftests

Upstream perfetto has dependencies on two new descriptor files:

* all_webview_metrics.descriptor
* trace_summary.descriptor

This adds their paths to the run_perfetto_diff_tests commandline.

Also changes run_perfetto_diff_tests to take a list of metrics
descriptors, instead of a separate argument for each, to cut down on the
boilerplate needed to add new descriptors.

PERFETTO_TESTS=Skipped because there are additional errors that need
fixing upstream.

Change-Id: I0b94487573e0c749b13e7c71498603e9826ee924
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6829711
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Auto-Submit: Joe Mason <joenotcharles@google.com>
Cr-Commit-Position: refs/heads/main@{#1499704}