Add verbose docs to `media-views.js`.

Props ericlewis.
See #30193.


git-svn-id: https://develop.svn.wordpress.org/trunk@30120 602fd350-edb4-49c9-b593-d223f7449a82
Bump db_version and add upgrade routine for schema change in [30056].

Fixes #22023.

git-svn-id: https://develop.svn.wordpress.org/trunk@30121 602fd350-edb4-49c9-b593-d223f7449a82