Add interactive mode for widget registration and rendering

[juliusknorr]

To cover nextcloud/server#42550 we need to extend the link preview components and API methods to:

• Allow registerWidget to let apps render a different view depending if an interactive widget was requested or not
• Allow the NcReferenceList to indicate if the shown widgets should be interactive or not
• Figure out a generic way to only render widgets in the visible area
• Check if we need a generic way to "enable" interactive mode on the fly to fix unexpected interactivity e.g. when scrolling through a talk room

[juliusknorr]

Reopening for the remaining two checkboxes