Refactor current "type testing" to rely on reflection-driven testing API

[idearat]

Our current "is*" testing and related low-level type checks etc. rely on a few large files. Refactor to:

• Support "sparse" definition. A new function to test should be able to define default results such that types which produce that result for that function don't need to be updated at all.
• Support "type specific descriptors", essentially a JSON file for each type/object being tested that the harness loads to let the system keep testing information in the type's bundle.

To accomplish this task we need to

• Complete Expand test harness's reflection approach to include "Exercisers" #568
• Refactor current bulk file(s) into their separate JSON test descriptor formats and distribute to the proper type bundle(s) or package(s).