Give each of Naggy/Nice/StrictMock a base class whose constructor runs before
the mocked class's constructor, and a destructor that runs after the mocked
class's destructor, so that any mock methods run in either the constructor or
destructor use the same strictness as other calls.
PiperOrigin-RevId: 348511612
Add static_asserts that verify that no class hierarchy contains more than one
of {NiceMock, NaggyMock, StrictMock}. This sort of nesting has always been
disallowed, but this CL adds a compile-time check to prevent it.
PiperOrigin-RevId: 347037822
