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.OpenGL/FormatInfo.cs

@@ -2,7 +2,7 @@ using OpenTK.Graphics.OpenGL;
 
 namespace Ryujinx.Graphics.OpenGL
 {
-    struct FormatInfo
+    readonly struct FormatInfo
     {
         public int  Components { get; }
         public bool Normalized { get; }