create test harness that confirm that tiered attribution is compatible with speculative attribution

Because of the characteristics of this test harness it will probably need to be defined as an external, non jtreg, test. The idea is to check the following, not a comprehensive list:

 - Types on the ASTs must be the same for both approaches just after the corresponding attribution approach ends
 - TA must execute the same unique type checks as SA during it's check phase, a different order is acceptable though
 - Propagation, or not, of stuck expressions to the corresponding enclosing context and their subsequent "unstucking" must be equivalent on both approaches