Widget permission prompt is too angry, not informative

[jryans]

We have a widget permission prompt that looks roughly like:

This is shown for anyone other than the person who added the widget the first time they encounter it for a given room. Once they allow, that is saved for that particular widget.

Some problems (taken from discussion in matrix-org/matrix-react-sdk#3243):

• It's unclear how this should fit in with in-progress IM terms flows (users might be prompted for both widget permission for a specific widget and terms for the IM server generally)
• The current design is somewhat angry with lots of "warning" and "be afraid"
• Other metadata could be useful here, such who added the widget, what type of widget is it, etc.
• It's unclear how to best present the URL without overwhelming users (only the origin part, only what fits on the first line, etc.)

[turt2live]

We iterated on this. Now it's too vague: #11471