Merge "tbs: Implement call join with conference call" am: cefaac5f

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2528939



Change-Id: I6453f19244a5aae51c4c7f832b44880533ad4334
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>