Remove Casts in Generated Code and Add FAWMN

[JasonBock]

Describe the solution you'd like
My notes are here. The first thing I need to do is see if this approach would perform better before I start modifying the generation. If that helps, then I'll make the full investment.

Describe alternatives you've considered
Leave things as-is.

[JasonBock]

I've done some perf work, and it looks like it's viable. I'm also going to change to FAWMN, which will also be a breaking change, but should be the right thing overall. Should also doc that developers should put all RockCreate<> or RockMake<> attributes in one file, and try to not duplicate any definitions. I could potentially create a diagnostic to warn developers when they do that, but that's minor.