TST/REF: Move static methods out of consistency classes
In order to keep such tests refactor PR more readable, in this PR, I only move those methods which are actually staticmethods out of huge consistency classes to be independent tests, so no code changes! And after this PR, the big consistency classes are broken down to much smaller.

This one will pave the way for replacing some other final fixtures & staticmethods out of classes 

cc @jreback 