Unify advertising API (3/3)

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: I899ed51bf4e747e1e3ff1a472a55f060249cbb75