Floss: Refactor DBus intf and only expose after interal API is ready am:...

Floss: Refactor DBus intf and only expose after interal API is ready am: a0c5c54a am: 2a580355 am: e47f3a2a am: 1c64e390 am: 5fbefc94

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2748695



Change-Id: I2d2a7c7f8c1445839ae2d7b7471e721636329720
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>