Keep only the classes in the android.test.mock package

framework-core-sources-for-test-mock has some classes that are outside
of the android.test.mock package. It is necessary just to provide
private APIs to the mock classes, but not to include them in the impl
library.

Removing the unnecessary classes by using jarjar.

Bug: 199529199
Test: m
Change-Id: I4d0de6132245c4923a4b17a4004c300cd864c116