Add defaults support for bootclasspath_fragment module type am: 9272dccb1e am: 9604b5571f

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2906878

Change-Id: Ife368da993d7f9c22568fdc091efac8e65a37315
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>