Break out RDFC-2019 verify tests by keyType

[tminard]

This PR:

• Breaks out the combined verifier keyType tests into one test PER keyType
• Asserts that implementations support suite keytypes (ignoring unsupported, and flagging missing)

I also did a bit of refactoring to make the tests way easier to follow and read.

if we like the approach, I'll move out some of the utils (inlined them for simplicity) and expand the pattern to the other *-verify tests.

Previous Results

New Results

Note that some existing implementations are failing. Should we update those implementations?