Abstract prebuilt_etc into prebuilt_file am: b81f77ed am: c0fa5fb3 am:...

Abstract prebuilt_etc into prebuilt_file am: b81f77ed am: c0fa5fb3 am: 30136e83 am: 90bdb0b4 am: 4b92ead0

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2002752



Change-Id: I51cf814d64aa0b68f23a69d3695a60c43621df3e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>