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: Ic1d0ef06e61f0ad4dcb07ed83d63de975d51c004
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>