Exposed setOptions via RTCPeerConnectionFactory

Exposed setOptions API for iOS SDK via RTCPeerConnectionFactory method
to provide ability to disable encryption and control which network
adapters are ignored.
Only subset of webrtc::PeerConnectionFactoryInterface::Options options
are exposed via iOS SDK, additional options can be exposed as requested.
Android SDK has already exposed setOption API via Java's PeerConnection
constructor, there changes provide similar functionaly to iOS SDK.

Bug: webrtc:8712
Change-Id: Ia2de38cf382afc1bad9bbec6c6eac21ad29aee89
Reviewed-on: https://webrtc-review.googlesource.com/34900
Commit-Queue: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21504}

sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnectionFactory.mm

@@ -10,6 +10,7 @@
 
 #import "RTCPeerConnectionFactory+Native.h"
 #import "RTCPeerConnectionFactory+Private.h"
+#import "RTCPeerConnectionFactoryOptions+Private.h"
 
 #import "NSString+StdString.h"
 #import "RTCAVFoundationVideoSource+Private.h"
@@ -242,6 +243,11 @@
                                            delegate:delegate];
 }
 
+- (void)setOptions:(nonnull RTCPeerConnectionFactoryOptions *)options {
+  RTC_DCHECK(options != nil);
+  _nativeFactory->SetOptions(options.nativeOptions);
+}
+
 - (BOOL)startAecDumpWithFilePath:(NSString *)filePath
                   maxSizeInBytes:(int64_t)maxSizeInBytes {
   RTC_DCHECK(filePath.length);