fix(core): Tightens the network stack (#479)

- [X] Removes network pause/resume
- [X] Adds back packet profiler
- [X] Adds state machine to keep track and trace netstates
- [X] Changes NetState.Running back to using an interlock exchange
- [X] Adds preliminary packet throttling support


### Packet Throttling
- `[GetThrottle <packetId>` to get the delay in milliseconds for that packet
- `[SetThrottle <packetId> <delay>` to set the delay in milliseconds for that packet
The settings are saved to `Configuration/throttles.json`

Projects/UOContent/Commands/SignParser.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.IO;
 using Server.Items;
+using Server.Network;
 
 namespace Server.Commands
 {
@@ -28,6 +29,8 @@ namespace Server.Commands
                 var list = new List<SignEntry>();
                 from.SendMessage("Generating signs, please wait.");
 
+                NetState.FlushAll();
+
                 using (var ip = new StreamReader(cfg))
                 {
                     string line;