Provide basic implementation of ITestBlock

Changing issue from original intent. Originally, this was to just provide an implementation of ITestBlock. I'm going to broaden this to a general "do v2".

We use some implementation of ILogger in the vast majority of test blocks. See if it makes sense to:
- Add ILogger to ITestBlock (potential issue of restricting how people want to consume ILogger in test blocks, since we support both property and constructor injection)
- Provide a basic ITestBlock implementation that has an ILogger attached in the primary use case (property injection). Allows people to use it or not.

Start by locating ITestBlock and the ILogger implementations used by test blocks. Resolve whether ILogger belongs on the interface and whether property or constructor injection is the intended primary use case; done means the agreed v2 design is implemented with a basic ITestBlock option.

Vom Indexierungsmodell aus dem Issue-Text verfasst.