[JSTEP-10] Add failing test utils

[JooHyukKim]

part of #1370.

Moving tests & cleaning up will follow

[cowtowncoder]

@JooHyukKim One idea -- not sure how easy to do, but possible -- it is possible to export and publish separate test jar by Maven, to share common test classes. If so, that should probably be done from jackson-core since almost everything else depends on it (directly or indirectly). If so, it could include these 3 classes, plus some version of current JUnit5TestBase (which can then be extended by module-specific classes like DatabindTestUtil)

[JooHyukKim]

Hmmmm, I clearly see how we could benefit from it. But I am not sure if it is more beneficial to do it during 2->3 transition phase.

I am concerned that it would sort of expand JSTEP-10's scope more, which also means we have less time to touch other TODO 3.0 things as well.

EDIT : Or maybe it actually is do the module thing now and I am not just aware of the reason?

[cowtowncoder]

@JooHyukKim Maybe we should allow bit of duplication at first, and get bigger conversion done now. And then test-jar publishing could be for 3.0 only, as the next step.

So let's defer reusability concern after more of conversion has been done.