[IncNTP] Add RevampedIncognitoView and use when flag is enabled.

This CL add new RevampedIncognitoView for incongito ntp revamp project
(go/incognito-ntp). New UI will be shown when incognito-ntp-revamp flag
is enabled. This CL copy-paste the legacy incognito_view, as follow-up
CLs will update the UI.

Bug: 1240087
Change-Id: I00a64eb9a58fa6f8668fedc4819811c3ce76f75a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3097507


Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Side YILMAZ <sideyilmaz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#918774}