Make RUN_SERIAL asserts more clear, reorganize unit tests some (trili…

…nos/Trilinos#7112)

Here, I make some of the asserts for the RUN_SERIAL tests hopefully a little
more clear (trilinos/Trilinos#7112).

As part of this I also reorgainized the unit tests some to group them better.
I broke off the RUN_SERIAL tests for TAAT() into thier own function.

However, more needs to be done to improve the organization of these tests and
make them more independent.  (What we really need is a proper unit test
harness for CMake code but that will take some work to create.)