Refactor merkletree tests
Refactor merkletree tests

Separate the test cases from TestVerify so that the test names reflect
the test case better.

PiperOrigin-RevId: 342152754

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor