aosp_arm64: add the android-4.19-stable Image.gz prebuilt am: b068fe1bc8 am: 7e0079fe88 am: dae08634d8

Original change: https://googleplex-android-review.googlesource.com/c/kernel/prebuilts/4.19/arm64/+/11885398

Change-Id: Iaf11aa384228f146863679947c9c44138eadc9f2