Convert the Android.mk of messagingtest to Android.bp am: ea4310bbc1

Original change: https://android-review.googlesource.com/c/platform/packages/apps/Messaging/+/2815927

Change-Id: I8eb5f8609a600820324e8ee49504ca3c431bc213
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>