fix(core): Core cleanup, adds event loop synchronization, and fixes gumps (#429)

- [X] Cleans up gump packets
- [X] Adds event loop task synchronization
- [X] Moves timer pause and cleans up the delay task timer class
- [X] Cleans up the conserve cpu
- [X] Renames variables to make them consistent with the new style
- [X] Removes process delta recursion checking.
- [X] Properly diposes net states. This fixes edge cases that may cause hanging connections to stay open longer than they should.
- [X] Fixes an issue with gump items not compiling properly

Users can now utilize `Timer.Pause()` since the code will be executed on the proper thread.

```cs
public void async void Talk()
{
    _canTalk = false;
    await Timer.Pause(Utility.RandomMinMax(5000, 8000)); // Talk after 5-8 seconds
    DoTalk();
    await Timer.Pause(Utility.RandomMinMax(12000, 25000)); // Reset ability to talk after 12-25 seconds
    _canTalk = true;
}
```

Projects/UOContent.Tests/UOContent.Tests.csproj

@@ -3,7 +3,7 @@
         <IsPackable>false</IsPackable>
     </PropertyGroup>
     <ItemGroup>
-        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.0-preview-20210106-01" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.8.3" />
         <PackageReference Include="Moq" Version="4.16.0" />
         <PackageReference Include="xunit" Version="2.4.1" />
         <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />