Adapter: Load native only with AdapterService

We should be able to initialized AdapterApp without bringing the whole
native. By moving the load library to AdapterService, we are opening
the possibility to have a service that does not depend on native.

Test: m Bluetooth
Test: Boot and check log for initialization order
Bug: 290403852
Change-Id: If25df66b4f6c7cece6dfcc289ee5d664133cfe93