Remove next/previous connections

[microbit-matt-hillsdon]

After discussion, for user testing we've ended up removing navigation to:

• next/previous connections
• statement inputs

This is on the basis that we're relying much more on move mode and less on specifying the correct insertion point up front.

We're using this monkey patch which also includes looping around (separate PR for that in core here). Deployment. Deployment that also has #465 for a more complete feel of where I'm aiming.

At some point there were options in the demo to remove at least next/previous connections. There is still vestigial UI in the demo but it doesn't work since the move of the LineCursor to core.

So we could just make this change in core or reinstate an option. I think the previous option isn't quite what we want, in that it kept a position at the end of a stack (whereas we now insert afterwards / end of statement input by default so it's not so relevant).

This is a somewhat tentative position in advance of user testing feedback, but we feel pretty confident and we discussed with @rachel-fenichel the need to make progress here ahead of the user testing report.

[rachel-fenichel]

I think the current status is that @gonfunko is attempting to remove next/previous connections and found that juggling the code back and forth between navigation policies and Cursor is more work than just putting all of it into navigation policies at this point.

Per discussion today, I support moving most of this code into the policies. The FocusManager tracks the state of the focused node, INavigable handles whether it is possible to navigate to a location (at a technical level), and navigation policies handle whether we actually want to navigate to a location (user-facing). The covers most of the responsibilities of the Cursor.

@gonfunko please confirm:

• If the above analysis is correct
• If you're working on this (set to In Progress if yes)
• If you think this is a breaking change and required in v12

[gonfunko]

Yes, this is largely correct; I may remove some methods from Cursor, and might refactor INavigable, so this probably is a bit breaking, albeit for new-in-v12 stuff.