Metrics: Add Bluetooth address obfuscator in Java

* Expose Bluetooth address obfuscator to Java layer as
  AdapterService.obfuscateAddress(BluetoothDevice)
* Add unit tests to verify different usage scenarios
* Add unit tests that read metrics salt value from disk and compare
  native layer obfuscation result with Java layer HMAC-SHA256
  calculation result

Bug: 112969790
Test: make, BluetoothInstrumentationTests
Change-Id: Iac151616413073b3602fd61d9e620a932ae0340c