R1:54f131dc4baa

Make "first broadcast" rules for Differential drafts more general

Summary:
See PHI228. Ref T2543. The current logic gets this slightly wrong: prototypes are off, you create a draft with `--draft`, then promote it with "Request Review". This misses both branches.

Instead, test these conditions a little more broadly. We also need to store broadcast state since `getIsNewObject()` isn't good enough with this workflow.

Test Plan:
- With prototypes on and autopromotion, got a rich email after builds…