Hide non-React widgets from the Select Widgets pane

Hi,

Mendix 10 is moving towards a React only front-end, when enabling "Use React client" in the app settings I would expect not just errors for widgets that are used but are not React widgets (current behaviour), but I would also like to see:

- Only list React widgets in the Select Widget window (filter the none react ones and allow to show them via a toggle/button)

- List warnings in the project for Widgets in the widget directory that are not React widgets and thus should be removed from the project

- Allow filtering in Marketplace content on React only

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