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/Translation/EmitterContext.cs

@@ -21,7 +21,7 @@ namespace Ryujinx.Graphics.Shader.Translation
 
         public int OperationsCount => _operations.Count;
 
-        private struct BrxTarget
+        private readonly struct BrxTarget
         {
             public readonly Operand Selector;
             public readonly int ExpectedValue;