GitLab

Specifically:
 - Deleting checked-in, settings/test_util.m.js
 - Auto-generate equivalent file at the correct location (one level up)
 - Update chrome://test references
 - Update BUILD.gn deps to depend on the js_modulizer() target, and
   ensure the generated file is available in test bots (via |data| deps)
 - Update test_data_source.cc to also look at gen/chrome/test/data/webui/
   when processing chrome://test requests

Bug: 965770
Change-Id: I6243986b3297fbb949220034fe88622adc320fa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1742832Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685275}