VideoPress: consider to address the whole connection/checkout flow from the VideoPress video block

Currently, when the site is not connected with dotcom, the Connection banner leads the user to the My Jetpack connection page, which is not harmful but kinda annoying for the users.

Let's try to handle the whole flow straight from the block editor.

Start at the VideoPress video block and trace the Connection banner's current link to the My Jetpack connection page. Map the connection and checkout states involved in the block editor, then confirm the intended complete flow with maintainers; done means an unconnected site can handle the flow from the block without the current detour.

Written by the indexing model from the issue text.