floss: Split out Advertiser code from bluetooth_gatt to bluetooth_adv

This patch doesn't yet make any DBus and behavior changes. The events
are still dispatched to bluetooth_gatt and then passed to bluetooth_adv.

Notable changes:
- Added IBluetoothAdvertiseManager trait and rename Advertisers to
  AdvertiseManager (follow Android naming)
- Deprecate *_sets_mut helpers because they hold the ownership of the
  whole structure and block the use of self.gatt.

Bug: 242083290
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: bluetooth_AdapterAdvHealth.all_floss
Flag: EXEMPT, Floss-only changes

Change-Id: I75a599a7ad825c07a108be31a213e6ae0dd532bf