Make interactive tests faster and support fresh namespaces.

Cuts off about 5-10% of unit test time.
Reuse existing module registry that is shared with all the other tests.
Fresh namespaces means that changes in one test do not affect other
tests.
Only bring in typed/racket/base so that it loads faster.
Make tr unit tests not run TR printer on test creation.

This makes it so that only running a subset of the tests is faster.
Simplify special-env-typecheck-tests and give them better names.
Make tests have better names and remove duplicates.
Improve compile-omit-paths for typed-racket tests.