[clang][dataflow] Add `SetupTest` parameter for `AnalysisInputs`.

Moves the work required for retrieving annotation states into the `SetupTest` and `PostVisitCFG` callback to avoid having to run a separate pass over the CFG after analysis has completed.

Reviewed By: gribozavr2, sgatev, ymandel

Differential Revision: https://reviews.llvm.org/D132377