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/CodeGen/Spirv/OperationResult.cs

@@ -3,7 +3,7 @@ using Spv.Generator;
 
 namespace Ryujinx.Graphics.Shader.CodeGen.Spirv
 {
-    struct OperationResult
+    readonly struct OperationResult
     {
         public static OperationResult Invalid => new OperationResult(AggregateType.Invalid, null);
 

Ryujinx.Graphics.Shader/CodeGen/Spirv/SpirvDelegates.cs

@@ -8,7 +8,7 @@ namespace Ryujinx.Graphics.Shader.CodeGen.Spirv
     /// <summary>
     /// Delegate cache for SPIR-V instruction generators. Avoids delegate allocation when passing generators as arguments.
     /// </summary>
-    internal struct SpirvDelegates
+    internal readonly struct SpirvDelegates
     {
         // Unary
         public readonly FuncUnaryInstruction GlslFAbs;

Ryujinx.Graphics.Shader/CodeGen/Spirv/TextureMeta.cs

@@ -1,33 +1,4 @@
-using System;
-
-namespace Ryujinx.Graphics.Shader.CodeGen.Spirv
+namespace Ryujinx.Graphics.Shader.CodeGen.Spirv
 {
-    struct TextureMeta : IEquatable<TextureMeta>
-    {
-        public int CbufSlot { get; }
-        public int Handle { get; }
-        public TextureFormat Format { get; }
-
-        public TextureMeta(int cbufSlot, int handle, TextureFormat format)
-        {
-            CbufSlot = cbufSlot;
-            Handle = handle;
-            Format = format;
-        }
-
-        public override bool Equals(object obj)
-        {
-            return obj is TextureMeta other && Equals(other);
-        }
-
-        public bool Equals(TextureMeta other)
-        {
-            return CbufSlot == other.CbufSlot && Handle == other.Handle && Format == other.Format;
-        }
-
-        public override int GetHashCode()
-        {
-            return HashCode.Combine(CbufSlot, Handle, Format);
-        }
-    }
+    readonly record struct TextureMeta(int CbufSlot, int Handle, TextureFormat Format);
 }