Move startAdvertising() logic into native code (2/3)

AdvertiseManager.startAdvertising() was implemented in Java layer for
historical reasons. Now that we have nice native callbacks and tests,
it can be moved into native code, where it will be shared between
Android daemon and bluetoothtbd.

Bug: 30622771
Test: native tests added to cover startAdvertising
Change-Id: Idf5d3c53b6ad21d8c7e239b5b150b88e073bb709