Provide basic implementation of ITestBlock

[PandaMagnus]

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.

[PandaMagnus]

Additional info: We recently had a need arise at a client where we need to know about a test within a test block. I'm thinking v2 is likely:

• Provide basic implementation of ITestBlock
• Need to update TestCaseException so it can aggregate both test block exceptions and finally block exceptions (and maybe a flag to alternatively fail or warn on finally block exceptions)
• Introduce a "Build" method on TestBuilder (I know, I know) that creates a TestCase object that is then added to the DI container before starting the test.
• "Build" maybe should also validate that every input is satisfied by something in the container or by a test block output
• For temporary backward compatibility, leave ExecuteTestCase on TestBuilder (may not make sense and lead people down the wrong path)