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/Translation/RegisterUsage.cs

@@ -114,7 +114,7 @@ namespace Ryujinx.Graphics.Shader.Translation
             }
         }
 
-        public struct FunctionRegisterUsage
+        public readonly struct FunctionRegisterUsage
         {
             public Register[] InArguments { get; }
             public Register[] OutArguments { get; }