requestMtu method
Requests a larger ATT MTU and returns the negotiated size.
Android honors mtu as the requested size. iOS has no CoreBluetooth API to request a
specific MTU -- it's negotiated automatically as part of connecting -- so on iOS this
only re-reads whatever was already negotiated and mtu is ignored.
Implementation
Future<int> requestMtu(int mtu) => BlueBreezePlatform.instance.deviceRequestMtu(id, mtu);