Add a couple testmode config tunables for debugging

[msullivan]

• __internal_no_apply_query_rewrites forces apply_query_rewrites to
  be false, disabling them in the same way that reflection queries
  do.
• Use the "reflection schema" as the base schema instead of the
  normal std schema. This allows looking at all the schema fields
  that are hidden in the public introspection schema.

Both of these (and especially the first) are things that I've
manually done in the code enough times that I've gotten fed up with
it.