GitLab

- The screen follows the current UX mock:
  https://docs.google.com/presentation/d/1DKXyhbIJYZ1V5846lOwingpV-64b-r2ItWAvSIjAjVk/edit#slide=id.g349a978079_0_290
- The screen grab consent text through assistant setting manager.
- After user opt-in the screen send the consent request through
  assistant settings manager.
- Import necessary proto files for the consent flow.

Bug: b/78190629
Test: Manual Test
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I963e56cb1467906f9e17d7a0217da8a81b7a77a8
Reviewed-on: https://chromium-review.googlesource.com/1035912
Commit-Queue: Yue Li <updowndota@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559566}