Frontend modules: AMP Compatibility

Let's ensure that all modules that currently output content to the frontend of a Jetpack site are currently compatible with the latest version of the AMP plugin, and do not generate any invalidation errors.

Here is the current list, sorted by a rough order of priority. Some of those may already be compatible.

- [x] WordPress.com Toolbar, aka Masterbar
- [x] Notifications
- [x] Stats
- [x] Photon
- [x] Related Posts
- [ ] Sharing
- [ ] Official buttons not all supported and / or hidden #12639
- [ ] Carousel #9557 and #17484
- [ ] Ads
- [ ] Widgets
- See #14398
- [ ] Search
- [ ] SEO Tools
- [ ] Comment Form
- [ ] Likes #9555
- [x] Comment Likes #9555 #14840
- [ ] Lazy Images
- [x] Jetpack Videos
- [ ] Google Analytics
- [ ] Shortcodes
- See #14397

- [ ] Gravatar Hovercards
- [ ] Infinite Scroll
- [ ] Tiled Gallery. Let's opt to support the block first. Legacy Tiled Galleries should not be as high on the priority list.
- [ ] Beautiful Math

Start by reviewing the unchecked modules in the issue, including Sharing, Carousel, Ads, Widgets, Search, SEO Tools, Comment Form, Likes, Lazy Images, Google Analytics, Shortcodes, Gravatar Hovercards, Infinite Scroll, Tiled Gallery, and Beautiful Math. Follow the referenced issues #12639, #9557, #17484, #14398, #9555, and #14397 where relevant. Done means the frontend modules work with the latest AMP plugin without invalidation errors.

Written by the indexing model from the issue text.