Context menu item for to/from underlying value

[ewpatton]

Describe the desired feature

I know this is out of scope for the original project, but it might be useful to have a context menu option that appears on blocks whose parent accepts an enum to swap to/from the underlying value. One concern I have is that people might get surprised when these fancy blocks show up in their project that weren't there before. Letting them have the option to go back to the number/text values may be useful. See how we do generic <=> specific blocks as an example.