Infinite Scroll: reverting [106807] until we can take a closer look. it was breaking themes with Masonry layouts. see #premiumthemes708

Merges r106990-wpcom.
Merge commit '9c603aa'
REST API: skip __do_not_document for /help endpoint

These should not be publicly visible.

https://[private link]

Merges r106845-wpcom.
REST API: abstract do_not_document check into a method

So we're not repeating code.

https://[private link]

Merges r106846-wpcom.
Merge commit '04a9d6f'
REST API

Handle deprectation and showing versions of other endpoints in the auto documentation. Since media has been versioned, and we want to document it, we need to be able to show those endpoints in the docs.

Merges r106930-wpcom.
REST API: Improvements to Jetpack Endpoints.
+ Add set autoupdate endpoints fort plugins and themes.
+ safehtml everything that comes from Jetpack sites.
+ Fix/add new tests.

props @rocco

Merges r107041-wpcom.
REST API
Media Endpoints (1.1)

Fix a few issues/bugs with the code: $insert was not defined as an empty array so attrs could get passed thru to other items. Also updated media_urls to associate errors with the correct index.
Finally made sure IDs are returned as ints like they are documented as.

Merges r107147-wpcom.
REST API: Fix inconsistency between me/sites and options.admin_url.

Force Jetpack site urls to http when the siteurl protcol is http.
+ remove wpcom custom filter when getting the theme stylesheet of a Jetpack site.

See: https://[private link]

Merges r106931-wpcom.
REST API
Media Endpoints

v1.1 of the listing endpoint was using 'numberposts' to set the number of requested items (because an earlier version of the code was using get_posts which is accepted). However, numberposts does not work for WP_Query. posts_per_page needs to be used instead.
Two tests have been added to MediaTest to make sure this works correctly.

Merges r107344-wpcom.
REST API: Fix how we generated featured_media for WPCOM posts

The find_featured_media function expected a normalized post response
but we were handing it a plain WP_Post object. Hand it the response
instead, so it can do its job.

See https://github.com/wordpress-mobile/WordPress-Android/issues/1940

Merges r107109-wpcom.
REST API: Turn off insertion of featured media for WP_Post objects

This is cauing some pretty nasty performance regressions.
See https://[private link]#/dashboard/db/rest-api-methods

Merges r107143-wpcom.