Overall; fixed design of IState.cs and IReadOnlyState.cs, and fixed namespaces in Beam.Abstractions to remove all references of Beam.Abstract.

Beam.Abstractions/IReadOnlyState.cs

@@ -1,6 +1,6 @@
-namespace Beam.Models;
+namespace Beam.Abstractions;
 
 public interface IReadOnlyState {
-    public string[] GetState();
-    IReadOnlyState Copy();
+    public ReadOnlySpan<string> GetState();
+    IState Copy();
 }