Add copy of LegacyBluetoothRouteController

This is a non-functional CL that allows subsequent reviews
to focus on the differences introduced in the new AudioPoliciesBluetoothRouteController, which is based on the
legacy implementation.

Bug: b/255495104
Test: N/A
Change-Id: I24396052871dd101eff9cae3942d12397f08fda2