system/common: Remove the BluetoothMetricsLogger helper

BluetoothMetricsLogger produces metrics logs that are packaged
into a protobuf binary using the format
system/gd/proto/metrics/bluetooth.proto

This legacy logging method is no longer use in practical
application and needs to be removed

Bug: 401588157
Test: m com.android.bt
Flag: EXEMPT, dead code removal
Change-Id: I827079276082460eceb9bee728ef25771bc5b5db