Adds tests for Install Scenarios to DexManagerTests

This CL moves the existing DexManagerTests into the Extended Mockito
directory, mocks out the relevant system services, and tests the
non-default Install Scenarios (as the default scenario is exercised by
the existing tests.)

Bug: 174783329
Test: atest DexManagerTests
Change-Id: Ie446ed748fc0b5690184c3a0a6498b82e8827181