Improve CheckCSMs test to check for overriding

CheckCSMs test intends to allow a white list of virtual methods; all other are expected to be static or final instance method.

JDK-8264774 has a sealed interface which defines caller-sensitive interface method. The test should be updated to allow CSM in a sealed interface if all implementations (all subclasses) of such CSM are final.

Currently the test does not fail if both interface and implementation methods are @CS annotated but fails if only interface is annotated.