Update cfe_assert/cfe_testrunner/cfe_testcase namespaces to match cFS suggested standard

[skliper]

Is your feature request related to a problem? Please describe.
From #1242, the cfe_testrunner entry point was too long, so namespace was adjusted to CFE_TR. cFS suggested namespace is typically just a couple characters (2-4).

Describe the solution you'd like
Adjust all three to shorter/consistent namespaces (module name, function names, globals, etc)

Describe alternatives you've considered
CFE_ASRT, CFE_TR, CFE_TC?

Additional context
#1242,

Requester Info
Jacob Hageman - NASA/GSFC