sepolicy: Add btnvtool to be part bluetooth domain

btnvtool needs qmux socket interaction to get the BT
address whcih is stored in modem nv.

btnvtool will be executed in the context of bluetooth.
It wiil fetch the addr from modem using QMI APIs.

New QMI interface has came up with the sepolicy.

Added the persist permission to bluetooth domain.

CRs-Fixed: 930130
Change-Id: I62b3538f750593e8fecf1068040b569f5a4253c4