Support a UI for creating and editing composite questions/components

[JaneSjs]

Original issue: T12189 - Registering a panel with inner questions as a custom component and a composite question at the same time doesn't work.

The task: allow survey creators to create composite components, such as a panel with questions inside. Survey creators would then have the option to save this as either a preconfigured item without the ability to modify inner elements, or as a custom toolbox item that can be reused and modified.

[JaneSjs]

+1 T14012 - Request for Question Import Feature in SurveyJS Creator https://surveyjs.answerdesk.io/internal/ticket/details/T14012

I noticed that none of these options are supported by the Form Builder, meaning, it seems that if one of our clients needs to construct a composite question called "Full Name" as the Demo suggests they need to do so programmatically since the JSON for the Form only references the "type" and the actual structure of the custom type itself is not defined inside of the Form JSON. It would be nice if the Form Builder would support creating these composite questions and then have their definitions be part of the JSON so no extra programmatic step is needed, any idea if this will be supported at some point?

[JaneSjs]

+1 T9559 - Is this available in v2 ? add 'Toolbox item ' https://surveyjs.answerdesk.io/internal/ticket/details/T9559

[JaneSjs]

+1 T16333 - allow user to modify custom component in form builder https://surveyjs.answerdesk.io/internal/ticket/details/T16333