[Flow202][lib][skip-ci] [17/23] Fix Flow issues in lib/shared/state-sync
Summary:
Similar to the preceding diff: Flow was printing errors because it was having trouble deducing the types for these selectors.
I extracted the selector definitions into their own variables so I could annotate them with specific types, which cleared the errors.
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 D9708
Test Plan: Confirm the Flow errors go away
Reviewers: tomek
Reviewed By: tomek
Subscribers: wyilio
Differential Revision: https://phab.comm.dev/D9709