Unify advertising API (1/3)

This patch unifies advertising API. On startup, if VSC multi advertising
is avaliable, it will be used, otherwise
BleAdvertiserLegacyHciInterfaceImpl will be used, which provides one
advertising instance.

Test: sl4a tests are passing, all proper tests updated accordingly
Change-Id: I73753962e3a33a980e8a9a1174c8d88611a47e6b