Bump to `2.14.0` - fixes issues related to `m4a` files.

Fixes #27570.



git-svn-id: https://develop.svn.wordpress.org/trunk@27811 602fd350-edb4-49c9-b593-d223f7449a82
When creating a new playlist, we don't know from the model what "type" it is right away (there is no longer a `video-playlist` shortcode) - we need to check the controller's library's prop for `type` when deciding what settings to display in the modal.

See #27535.



git-svn-id: https://develop.svn.wordpress.org/trunk@27812 602fd350-edb4-49c9-b593-d223f7449a82
Return the default mime icon for playlist items that don't have a featured image in `wp_prepare_attachment_for_js()`.

See [27640].



git-svn-id: https://develop.svn.wordpress.org/trunk@27813 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Set hightlight color to blue. Same color as in [27741].

fixes #27358.

git-svn-id: https://develop.svn.wordpress.org/trunk@27814 602fd350-edb4-49c9-b593-d223f7449a82
Introduce `pre_update_option` filter.

Filter is available in update_option() and allows to filter any option before its value is (maybe) serialized and updated.

see #27504.
props westonruter.


git-svn-id: https://develop.svn.wordpress.org/trunk@27815 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Convert static WP_Customize_Widgets class into instantiated class and merge Options_Transaction into WP_Customize_Widgets.

see #27504.
props westonruter.


git-svn-id: https://develop.svn.wordpress.org/trunk@27816 602fd350-edb4-49c9-b593-d223f7449a82
MediaElement.js: Update version for [27811]. see #27570.

git-svn-id: https://develop.svn.wordpress.org/trunk@27817 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Remove `UPDATE_WIDGET_AJAX_ACTION` and `UPDATE_WIDGET_NONCE_POST_KEY` constants.

see #27534.

git-svn-id: https://develop.svn.wordpress.org/trunk@27818 602fd350-edb4-49c9-b593-d223f7449a82
Widget Customizer: Simplify nonces.

see #27534.

git-svn-id: https://develop.svn.wordpress.org/trunk@27819 602fd350-edb4-49c9-b593-d223f7449a82
Merge branch 'master' into trac-27491