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/Decoders/Decoder.cs

@@ -473,7 +473,7 @@ namespace Ryujinx.Graphics.Shader.Decoders
             op = Unsafe.As<ulong, T>(ref rawOp);
         }
 
-        private struct BlockLocation
+        private readonly struct BlockLocation
         {
             public Block Block { get; }
             public int Index { get; }