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.Vulkan/DisposableFramebuffer.cs

@@ -3,7 +3,7 @@ using System;
 
 namespace Ryujinx.Graphics.Vulkan
 {
-    struct DisposableFramebuffer : IDisposable
+    readonly struct DisposableFramebuffer : IDisposable
     {
         private readonly Vk _api;
         private readonly Device _device;