Add empty system and module-lib APIs for conscrypt

These are needed for backwards compatibility checks in conscrypt when
adding system and module-lib API surfaces.

Bug: 216435117
Test: m conscrypt-module-sdk
      - Verify the snapshot includes system and module-lib API files.
      - Without these changes the build fails with missing filegroups.
Change-Id: If88db3b1e822b6a7d682c83be6c407a550a24410
4 files changed