JNI+mm: Generate certificate if non-default key type is specified.

By comparing key type with KT_DEFAULT we remove the implicit assumption that
the default is RSA.

Removing the assumptions about what the default is is necessary for a
follow-up CL that will change the default.

BUG=webrtc:5795, webrtc:5707
R=hta@webrtc.org, magjed@webrtc.org, tommi@webrtc.org
TBR=tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1965313002 .

Cr-Commit-Position: refs/heads/master@{#12722}

webrtc/sdk/objc/Framework/Classes/RTCConfiguration+Private.h

@@ -21,7 +21,7 @@ NS_ASSUME_NONNULL_BEGIN
  * needed to pass to the underlying C++ APIs.
  */
 @property(nonatomic, readonly)
-    webrtc::PeerConnectionInterface::RTCConfiguration nativeConfiguration;
+    webrtc::PeerConnectionInterface::RTCConfiguration* nativeConfiguration;
 
 + (webrtc::PeerConnectionInterface::IceTransportsType)
     nativeTransportsTypeForTransportPolicy:(RTCIceTransportPolicy)policy;