* Introduce `customize_post_value_set_{$setting_id}` and `customize_post_value_set` actions which are done when `WP_Customize_Manager::set_post_value()` is called.
* Clear the `preview_applied` flag for aggregated multidimensional settings when a post value is set. This ensures the new value is used instead of a previously-cached previewed value.
* Move `$is_preview` property from subclasses to `WP_Customize_Setting` parent class.
* Deferred preview: Ensure that when `preview()` short-circuits due to not being applicable that it will be called again later when the post value is set.
* Populate post value for updated-widget with the (unsanitized) JS-value in `WP_Customize_Widgets::call_widget_update()` so that value will be properly sanitized when accessed in `WP_Customize_Manager::post_value()`.
Includes unit tests with assertions to check the reported issues and validate the fixes.
Fixes defect introduced in [35007].
See #32103.
Fixes#34738.
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git-svn-id: http://core.svn.wordpress.org/trunk@35688 1a063a9b-81f0-0310-95a4-ce76da25c4cd