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.Memory/Range/MultiRange.cs

@@ -6,7 +6,7 @@ namespace Ryujinx.Memory.Range
     /// <summary>
     /// Sequence of physical memory regions that a single non-contiguous virtual memory region maps to.
     /// </summary>
-    public struct MultiRange : IEquatable<MultiRange>
+    public readonly struct MultiRange : IEquatable<MultiRange>
     {
         private readonly MemoryRange _singleRange;
         private readonly MemoryRange[] _ranges;