Do not use registerStateChangeCallback from the app

This method is made for apps/framework to get Bluetooth state update.
The expected flow is: app -> service -> framework.

Calling this in the app means that we are doing: app -> service -> app.

This commit instead remove going to the service by registering a local
callback in the app instead.

Bug: 262605980
Test: m com.android.btservices
Change-Id: I74dceab111a66bbb202953a93aa028dac225b087