Make structs readonly when applicable (#4002)

* Make all structs readonly when applicable. It should reduce amount of needless defensive copies

* Make structs with trivial boilerplate equality code record structs

* Remove unnecessary readonly modifiers from TextureCreateInfo

* Make BitMap structs readonly too

Ryujinx.Graphics.Shader/StructuredIr/StructuredProgramInfo.cs

@@ -2,7 +2,7 @@ using System.Collections.Generic;
 
 namespace Ryujinx.Graphics.Shader.StructuredIr
 {
-    struct TransformFeedbackOutput
+    readonly struct TransformFeedbackOutput
     {
         public readonly bool Valid;
         public readonly int Buffer;