feat: Adds .NET 7 & Arm64 support (#1229)

## BREAKING CHANGE
**Publishing for linux will no longer include runtimes**

## Major Changes
* Adds .NET 7 support.
* Adds ARM64 support (experimental).
* Changes linux support to be open-ended against anything .NET 7 supports.
* Fixes native library resolutions. (Make sure to install `dev` versions of the libraries)
* Updates README
* Adds Ubuntu 22, CentOS 8/9 Stream to CI/CD.

## TODOs:
* Update modernuo.com docs

Closes #1173
Closes #1159

Projects/Server/Gumps/GumpImageTileButton.cs

@@ -61,11 +61,7 @@ public class GumpImageTileButton : GumpEntry
 
     public int Height { get; set; }
 
-#if NET7_SDK
     public override void AppendTo(ref SpanWriter writer, OrderedHashSet<string> strings, scoped ref int entries, scoped ref int switches)
-#else
-    public override void AppendTo(ref SpanWriter writer, OrderedHashSet<string> strings, ref int entries, ref int switches)
-#endif
     {
         writer.WriteAscii(
             $"{{ buttontileart {X} {Y} {NormalID} {PressedID} {(int)Type} {Param} {ButtonID} {ItemID} {Hue} {Width} {Height} }}"