Add ability to transform video block to VideoPress

[SiobhyB]

Is your feature request related to a problem? Please describe.

By default, both the web and the apps convert video blocks to VideoPress v5. However, the VideoPress block used VideoPress v6. On the web, there's a fairly prominent nudge for users to do convert the video block to the VideoPress block, but no similar option exists in the app:

Describe the solution you'd like

It would be good to at least allow the ability to transform the video block to VideoPress in the "Transform block" menu.

Describe alternatives you've considered

We could also consider adding a more prominent nudge for transforming the block, similar to the web, though this would require design input.