Send back setting validities with full refreshes and selective refreshes so that invalid settings can have notifications displayed immediately before attempting save, and so that these notifications can be cleared as soon as the input is corrected.
* Splits out JS logic for listing controls into separate methods `wp.customize.Setting.prototype.findControls()` and `wp.customize.findControlsForSettings()`.
* Adds a `setting` property to the `data` on notifications added to controls that are synced from their settings.
* Adds `selective-refresh-setting-validities` message sent from preview to pane.
* Changes `WP_Customize_Manager::validate_setting_values()` to return when settings are valid as well as invalid.
* Adds `WP_Customize_Manager::prepare_setting_validity_for_js()`.
* Add setting validities to data exported to JS in Customizer Preview and in selective refresh responses.
Fixes#36944.
Built from https://develop.svn.wordpress.org/trunk@37700
git-svn-id: http://core.svn.wordpress.org/trunk@37666 1a063a9b-81f0-0310-95a4-ce76da25c4cd
