Simplify class redefinition.

- For debuggable apps, do not compile with compact dex.
- Eagerly return the dex file (and don't do lazy unquickening) in
  ArtClassDefinition.

Test: cpct/carservice/carservice_test
Test: suite/test-mapping-presubmit-retry_cloud-tf
Test: unbundled/launcher/nexus_unit_test_multi_device_platform
Test: FrameworksIkeTests:com.android.internal.net.eap.test.EapMsChapV2Test
Test: test.py

Bug: 196414062

Change-Id: I45ae220fa62aa41ff5fd8dd0e893090842ee18a6