feat: add loopback when finding a valid node during a keyboard drag

[rachel-fenichel]

• Fixes Add helpers to loop around from the last block of the workspace to the first (and vice versa) when doing constrained movement. #369
• Fixes Remove or improve workspace positions in constrained move #396

Proposed followup

• Add tests for loopback search (Add tests for cursor loopback during drag #410)
• Move loopback code to core
• Use loopback code for navigation as well as for dragging

Additional information

The first commit handles loopback; the second commit cleans up some lint.

[rachel-fenichel]

Build fails on this because it relies on a paired change in core (RaspberryPiFoundation/blockly#8883) and was developed by linking against core. I have checked that the tests pass and done some basic manual testing.