Fixes an issue with flow analysis where branches within `try` could be considered as going through `finally`

    We could incorrectly assume that variable is assigned (or unassigned in async capture tracking case).

    As a resutl we could
    - allow use of unassigned locals (undefined behavior)
    - not capture a local whose value survives `await` (NRE crash)

    Also added a regression test fro VB, which does not seem affected.

    Fixes:#19831