Add Group Id to PhoneAccount

Add an api to set a group Id to a PhoneAccount. This functions as
a marker that tells Telecom to replace an old registered PhoneAccount
with a newly registered PhoneAccount if their Group Id is the same. This
allows us to handle transparent PhoneAccount switching in Telecom
without losing user specified enabled settings and user calling account
defaults.

Bug: 28173788
Change-Id: I270e766347d7f817c94f86503db2cdb1f93dafa4