feat(messaging, ios): Support get notification raw data

[zeqinjie]

Description

Support to get the messaging notification raw data to support apple push, but now it was RemoteNotification object.

  /// Constructs a [RemoteMessage] from a raw Map.
  factory RemoteMessage.fromMap(Map<String, dynamic> map) {
    return RemoteMessage(
      senderId: map['senderId'],
      category: map['category'],
      collapseKey: map['collapseKey'],
      contentAvailable: map['contentAvailable'] ?? false,
      data: map['data'] == null
          ? <String, dynamic>{}
          : Map<String, dynamic>.from(map['data']),
      from: map['from'],
      // Note: using toString on messageId as it can be an int or string when being sent from native.
      messageId: map['messageId']?.toString(),
      messageType: map['messageType'],
      mutableContent: map['mutableContent'] ?? false,
      notification: map['notification'] == null
          ? null
          : RemoteNotification.fromMap(
              Map<String, dynamic>.from(map['notification'])),
      // Note: using toString on sentTime as it can be an int or string when being sent from native.
      sentTime: map['sentTime'] == null
          ? null
          : DateTime.fromMillisecondsSinceEpoch(
              int.parse(map['sentTime'].toString())),
      threadId: map['threadId'],
      ttl: map['ttl'],
    );
  }

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