Allow users to override default gallery settings in JS via `wp_localize_script()`. This is already possible in PHP by filtering `shortcode_atts_gallery`.

Fixes #28693.

Built from https://develop.svn.wordpress.org/trunk@28990


git-svn-id: http://core.svn.wordpress.org/trunk@28778 1a063a9b-81f0-0310-95a4-ce76da25c4cd
The MCE view for galleries needs to read `wp.media.galleryDefaults.columns` after [28990].

See #28693.

Built from https://develop.svn.wordpress.org/trunk@28991


git-svn-id: http://core.svn.wordpress.org/trunk@28779 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Make a new file: `media-grid.js`. This will be way more useful in later commits and help reduce churn and bloat in `media-views.js`.

See #24716.

Built from https://develop.svn.wordpress.org/trunk@28992


git-svn-id: http://core.svn.wordpress.org/trunk@28780 1a063a9b-81f0-0310-95a4-ce76da25c4cd