R1:38e788c99a78

Partially decouple revision broadcasting from revision draft state

Summary:
Depends on D19283. Ref T13110. To enable "Changes Planned + But, Still A Draft" and "Abandoned + But, Never Promoted From Draft" states, decouple the "broadcast" flag from the "draft" state.

Broadcast behavior is now based only on the `shouldBroadcast` flag, and revisions in any state may have this flag.

Revisions gain this flag when created as a non-draft, or when they leave the draft state for the first time.

There are…