fix(core): Adds SkipLocalsInitAttribute support, optimizes broadcasted packets (#363)

- [X] Adds support for `SkipLocalsInitAttribute`. SkipLocalsInitAttribute skips initializing stack variables including `stackalloc`. I don't think it is wired/working yet but should be implemented soon.
- [X] Optimizes broadcasted packets by checking if the first byte (packet ID) is non-zero. If it is already set, it reuses the buffer.
- [X] Removes unnecessary refs to Spans. I don't think the Span struct itself is mutable, so a ref is not helpful.

Projects/Server/Sector.cs

@@ -96,7 +96,7 @@ namespace Server
 
                 if (index >= 0)
                 {
-                    list[index] = newValue;
+                    list![index] = newValue;
                 }
                 else
                 {