Combine testComplexCast with testCast (facebookincubator#8254)

Summary:
Combines `testComplexCast` and `testCast` into one to reduce redundant
interfaces. Some differences, including the test of input vector not being
changed after the evaluation, and caller specified nullOnFailure test, are
supported in `testCast` method. Removes `fromType` and `toType` parameters
from `testCast` method, as they can be deduced from input and expected
vectors.

Pull Request resolved: facebookincubator#8254

Reviewed By: xiaoxmeng

Differential Revision: D53107665

Pulled By: kagamiori

fbshipit-source-id: ddc4379eeb33e336bab2b0fab9760252a2421bf6