Stop using deprecated constraints-based version of CreateAudioSource.

Also did some slight refactoring of the code that turns constraints
into rtc::Optionals. Used a template method to avoid code duplication,
and used the same pattern for "CopyConstraintsIntoAudioOptions" as was
being used for "CopyConstraintsIntoRtcConfiguration".

BUG=webrtc:6752

Review-Url: https://codereview.webrtc.org/2628523003
Cr-Commit-Position: refs/heads/master@{#16063}

webrtc/sdk/android/src/jni/peerconnection_jni.cc

@@ -1442,8 +1442,10 @@ JOW(jlong, PeerConnectionFactory_nativeCreateAudioSource)(
       new ConstraintsWrapper(jni, j_constraints));
   rtc::scoped_refptr<PeerConnectionFactoryInterface> factory(
       factoryFromJava(native_factory));
+  cricket::AudioOptions options;
+  CopyConstraintsIntoAudioOptions(constraints.get(), &options);
   rtc::scoped_refptr<AudioSourceInterface> source(
-      factory->CreateAudioSource(constraints.get()));
+      factory->CreateAudioSource(options));
   return (jlong)source.release();
 }