Minor ObjC API tweaks.

Adds setConfiguration back and renames statsId back to reportId.

BUG=

Review URL: https://codereview.webrtc.org/1778033002

Cr-Commit-Position: refs/heads/master@{#11936}
diff --git a/webrtc/api/objc/RTCStatsReport.h b/webrtc/api/objc/RTCStatsReport.h
index fc66faf..f3f8907 100644
--- a/webrtc/api/objc/RTCStatsReport.h
+++ b/webrtc/api/objc/RTCStatsReport.h
@@ -22,7 +22,7 @@
 @property(nonatomic, readonly) NSString *type;
 
 /** The identifier for this object. */
-@property(nonatomic, readonly) NSString *statsId;
+@property(nonatomic, readonly) NSString *reportId;
 
 /** A dictionary holding the actual stats. */
 @property(nonatomic, readonly) NSDictionary<NSString *, NSString *> *values;