fix(auth, ios): deprecate MultifactorInfo.enrollmentDate should be enrollmentTime (#7653)

rename `enrollmentDate` -> `enrollmentTime` on iOS to match Android/Web
(ref: https://firebase.google.com/docs/reference/js/auth.multifactorinfo)

keep `enrollmentDate` around on ios for backwards compatibility, mark as
deprecated.

ref:
- https://github.com/invertase/react-native-firebase/blob/main/packages/auth/android/src/main/java/io/invertase/firebase/auth/ReactNativeFirebaseAuthModule.java#L2500
- https://github.com/invertase/react-native-firebase/blob/main/packages/auth/lib/index.d.ts#L483

split from #7565

Author: mnahkies

packages/auth/ios/RNFBAuth/RNFBAuthModule.m

@@ -1686,13 +1686,15 @@ - (NSDictionary *)firebaseUserToDict:(FIRUser *)user {
   NSMutableArray *enrolledFactors = [NSMutableArray array];
 
   for (FIRPhoneMultiFactorInfo *hint in hints) {
-    NSString *enrollmentDate =
+    NSString *enrollmentTime =
         [[[NSISO8601DateFormatter alloc] init] stringFromDate:hint.enrollmentDate];
     [enrolledFactors addObject:@{
       @"uid" : hint.UID,
       @"factorId" : [self getJSFactorId:(hint.factorID)],
       @"displayName" : hint.displayName == nil ? [NSNull null] : hint.displayName,
-      @"enrollmentDate" : enrollmentDate,
+      @"enrollmentTime" : enrollmentTime,
+      // @deprecated enrollmentDate kept for backwards compatibility, please use enrollmentTime
+      @"enrollmentDate" : enrollmentTime,
     }];
   }
   return enrolledFactors;
@@ -1745,4 +1747,4 @@ - (FIRActionCodeSettings *)buildActionCodeSettings:(NSDictionary *)actionCodeSet
   return settings;
 }
 
-@end
+@end