[native][web] Cast InputState / BaseInputState when returning from selectors

Summary:
While working on the unused-promise Flow lint (in particular, D10162) I noticed that Flow was failing to typecheck the return value of these selectors.

Adding this cast fixed the issue, and things appear to be typechecked correctly now.

(@atul, this was the change that previously caused minimallyEncoded type errors for me, but no longer does after rebasing.)

Depends on D10167

Test Plan: Flow

Reviewers: atul

Reviewed By: atul

Subscribers: tomek, atul

Differential Revision: https://phab.comm.dev/D10168