* When the media-type is changed, there is a new `onChangeMediaType` method to handle actions.
* If target schema properties key/value pairs does NOT equals current schema properties, clear the requestBodyValue, try-it-out request/response and validation params.
* If target schema properties key/value pairs DOES equals current schema properties, do not change or re-render schema properties
* oas3Selector `validateShallowRequired` now also validates required keys against target media-type
Fixes#6201, #6250, #6476
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