Unify the Android Rich NTT for reuse on iOS The current PR is pre-requisite of Dynamic NTT on iOS as it allows to reuse android `New Tab Takeover WebUI` on iOS. The PR removes dependency of android `New Tab Takeover WebUI` from `ViewCounterService` which is not available on iOS. It also removes `current_wallpaper` base::Value cache in ViewCounterService which allows to save memory and makes code cleaner.