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/TextureCache.cs

@@ -16,7 +16,7 @@ namespace Ryujinx.Graphics.Gpu.Image
     /// </summary>
     class TextureCache : IDisposable
     {
-        private struct OverlapInfo
+        private readonly struct OverlapInfo
         {
             public TextureViewCompatibility Compatibility { get; }
             public int FirstLayer { get; }