[ads] iOS unification

[tmancey]

• [x] [ads] Unify iOS prerequisites
• [x] [ads] Unify iOS prefs
• [x] [ads] Unify iOS HTTP_UPGRADE_REQUIRED
• [x] [ads] Unify iOS adaptive captcha will be resolved by https://github.com/brave/brave-browser/issues/33969
• [x] [ads] Unify iOS reminders
• [x] [ads] Unify iOS update rewards
• [x] [ads] Unify iOS new tab page ad serving
• [x] [ads] Unify iOS search result attribution
• [ ] [ads] Unify iOS component updater
• [ ] [ads] Unify iOS service layer
• [ ] [ads] Unify iOS common operations
• [ ] [ads] Unify iOS P2A
• [ ] [ads] Unify iOS pref migration
• [ ] [ads] Unify iOS Browsing History
• [ ] [ads] Unify iOS federated learning
• [ ] [ads] Unify iOS save ad
• [ ] [ads] Unify iOS mark ad as inappropriate
• [ ] [ads] Unify iOS like/dislike category

--

https://github.com/brave/brave-browser/projects/26#column-19651416

--

As part of the above, we will also work on browser layer issues; see https://github.com/brave/brave-browser/projects/26#column-19667912.