OnionSoup: Move web_feature.mojom in public/platform to public/mojom

This CL moves web_feature.mojom in public/platform to
public/mojom/web_feature and updates paths for web_feature.mojom.

It also moves PRESUBMIT.py for web_feature.mojom to
public/mojom/web_feature.

Bug: 919393
Change-Id: I1d22645fdd081a81bf18a85511d208c2e7b0bf7a
Reviewed-on: https://chromium-review.googlesource.com/c/1488487
Commit-Queue: Julie Jeongeun Kim <jkim@igalia.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636661}
53 files changed