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.Gpu/Image/TextureGroup.cs

@@ -14,7 +14,7 @@ namespace Ryujinx.Graphics.Gpu.Image
     /// <summary>
     /// An overlapping texture group with a given view compatibility.
     /// </summary>
-    struct TextureIncompatibleOverlap
+    readonly struct TextureIncompatibleOverlap
     {
         public readonly TextureGroup Group;
         public readonly TextureViewCompatibility Compatibility;