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.HLE/HOS/ModLoader.cs

@@ -36,7 +36,7 @@ namespace Ryujinx.HLE.HOS
         private const string AmsNroPatchDir = "nro_patches";
         private const string AmsKipPatchDir = "kip_patches";
 
-        public struct Mod<T> where T : FileSystemInfo
+        public readonly struct Mod<T> where T : FileSystemInfo
         {
             public readonly string Name;
             public readonly T Path;