gdb: more cleanups

- convert GdbRegisters utilities into extensions on IExecutionContext

- add a Write/Read Register helper on Debugger that handles 32/64 bit instead of doing that for every usage of register reading/writing

src/Ryujinx.HLE/Debugger/RegisterInformation.cs

@@ -17,12 +17,9 @@ namespace Ryujinx.HLE.Debugger
 
         private static string GetEmbeddedResourceContent(string resourceName)
         {
-            Stream stream = System.Reflection.Assembly.GetExecutingAssembly().GetManifestResourceStream("Ryujinx.HLE.Debugger.Gdb.Xml." + resourceName);
-            StreamReader reader = new(stream);
-            string result = reader.ReadToEnd();
-            reader.Dispose();
-            stream.Dispose();
-            return result;
+            using Stream stream = System.Reflection.Assembly.GetExecutingAssembly().GetManifestResourceStream("Ryujinx.HLE.Debugger.Gdb.Xml." + resourceName);
+            using StreamReader reader = new(stream);
+            return reader.ReadToEnd();
         }
     }
 }