Add a method to clear cached variants from SearchVariant, and a configuration flag for whether
a variant should be enabled or not. Add a FullTextSearch TestState class which will globally
disable the queuedjobs and fulltextsearch shutdown handlers during tests, and is not used to
clear cached variants on each test to prevent global state leakage.
Also removes Phockito as a test dependency.
Steve Boyd
Robbie Averill
Raissa North