Use LE transport when Headtracker service is available

Test: mmm packages/modules/Bluetooth
Test: manual | Pair with buds supporting Android Headtracker service
Flag: com.android.bluetooth.flags.android_headtracker_service
Bug: 332590397
Bug: 335708774
Change-Id: Id1eda9565a0fe97d7bce699a743ab42fa1ac255c