The MR adds implementations (+ a few tests) for the following methods in `bluetoothapis.h`:
* `BluetoothSdpEnumAttributes` * `BluetoothSdpGetContainerElementData` * `BluetoothSdpGetElementData` * `BluetoothSdpGetAttributeValue`
-- v3: bluetoothapis/tests: Add test for BluetoothSdpGetAttributeValue. bluetoothapis: Implement BluetoothSdpGetAttributeValue. bluetoothapis/tests: Add unit tests for BluetoothSdpEnumAttributes, BluetoothSdpGetContainerElementData, and BluetoothSdpGetElementData.