GitLab

- Deleted manifest.json, pwa.html
- Populated WebApplicationInfo with values from manifest.json
- Updated installation for Help app in CreateSystemWebApps

Bug: b/168159973
Change-Id: I3106cd8eba5806762afd24ce36b9ff522e93b375
Cq-Include-Trybots: chrome/try:linux-chromeos-chrome
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2428490Reviewed-by: Rachel Carpenter <carpenterr@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Auto-Submit: Callistus Tan <callistus@google.com>
Commit-Queue: Callistus Tan <callistus@google.com>
Cr-Commit-Position: refs/heads/master@{#811096}