The new version of Flow seems to want all new Promise instantiations to be parameterized with the promise's type. It also wants some more typehints in places where it can't deduce the correct type param for Promise.
This is the native equivalent of D9779 (web) and D9711 (lib).
NOTE: CI will fail on this diff. I considered the possibility of fixing Flow errors BEFORE upgrading Flow, but it wasn't possible... in some cases, the fixes to support the new version of Flow caused errors in the old version. I could have hidden these type errors with $FlowFixMe lines and then later revert those, but that seemed like too much busy work.
Depends on D10038