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.Cpu/ExceptionCallbacks.cs

@@ -17,7 +17,7 @@ namespace Ryujinx.Cpu
     /// <summary>
     /// Stores handlers for the various CPU exceptions.
     /// </summary>
-    public struct ExceptionCallbacks
+    public readonly struct ExceptionCallbacks
     {
         /// <summary>
         /// Handler for CPU interrupts triggered using <see cref="IExecutionContext.RequestInterrupt"/>.