NetworkServer SendToAll does not check size of message before sending

[James-Frowen]

Describe the bug
When NetworkServer.SendToAll is called it does not check the size before calling conn.Send(ArraySegment...). This can cause large message to be added to batches which will then result in unhelpful errors:

NetworkConnection.ValidatePacketSize: cannot send packet larger than 64350 bytes, was 5746485 bytes
UnityEngine.Debug:LogError (object)
Mirror.NetworkConnection:ValidatePacketSize (System.ArraySegment`1<byte>,int) (at Assets/Plugins/Mirror/Core/NetworkConnection.cs:104)
Mirror.NetworkConnection:Update () (at Assets/Plugins/Mirror/Core/NetworkConnection.cs:190)
Mirror.NetworkConnectionToClient:Update () (at Assets/Plugins/Mirror/Core/NetworkConnectionToClient.cs:181)
Mirror.NetworkServer:Broadcast () (at Assets/Plugins/Mirror/Core/NetworkServer.cs:1703)
Mirror.NetworkServer:NetworkLateUpdate () (at Assets/Plugins/Mirror/Core/NetworkServer.cs:1777)
Mirror.NetworkLoop:NetworkLateUpdate () (at Assets/Plugins/Mirror/Core/NetworkLoop.cs:206)

[IMPORTANT] How can we reproduce the issue, step by step:

• call NetworkServer.SendToAll<MyMessage>(...) with a message that is bigger than transport can send

Expected behavior
SendToAll should check size (by calling ValidatePacketSize ?). and log error with the stack that will tell user what message is too big, for example:

...
Mirror.NetworkServer:SendToAll<MiscInfoMessage> (MiscInfoMessage,int,bool) (at Assets/Plugins/Mirror/Core/NetworkServer.cs:453)
NetworkCommands:UserCode_CmdSetLevelInformation__LevelInformationDataSO (LevelInformationDataSO) (at Assets/Scripts/Utility/NetworkCommands.cs:571)
...

This will then allow user to track down what is sending it

Desktop (please complete the following information):

• Mirror branch: v78.3.0
  Looks like it would be a problem in v86.14.0, but I havn't tested that

Additional context

source:

Mirror/Assets/Mirror/Core/NetworkServer.cs

Lines 478 to 497 in 325cc15

	{
	// pack message only once
	NetworkMessages.Pack(message, writer);
	ArraySegment<byte> segment = writer.ToArraySegment();
	// filter and then send to all internet connections at once
	// -> makes code more complicated, but is HIGHLY worth it to
	// avoid allocations, allow for multicast, etc.
	int count = 0;
	foreach (NetworkConnectionToClient conn in connections.Values)
	{
	if (sendToReadyOnly && !conn.isReady)
	continue;
	count++;
	conn.Send(segment, channelId);
	}
	NetworkDiagnostics.OnSend(message, channelId, segment.Count, count);
	}

[miwarnec]

fixed