More useful Union simplification.

From Typed Racket: https://github.com/plt/racket/commit/beefe73f7e7b6fbb547f327e206f447e4f6815b0
Clean up internal local annotations
Disable tests related to CTYP-140
Preliminary macros for filter/remove. Pending CTYP-141
Make sure we always do an expected check for a top level check-form