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.HLE/HOS/Kernel/Common/KernelInit.cs

@@ -5,7 +5,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Common
 {
     static class KernelInit
     {
-        private struct MemoryRegion
+        private readonly struct MemoryRegion
         {
             public ulong Address { get; }
             public ulong Size    { get; }

Ryujinx.HLE/HOS/Kernel/Common/OnScopeExit.cs

@@ -2,7 +2,7 @@
 
 namespace Ryujinx.HLE.HOS.Kernel.Common
 {
-    struct OnScopeExit : IDisposable
+    readonly struct OnScopeExit : IDisposable
     {
         private readonly Action _action;
         public OnScopeExit(Action action) => _action = action;

Ryujinx.HLE/HOS/Kernel/Ipc/KServerSession.cs

@@ -17,7 +17,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Ipc
             (MemoryState)0xfffce5d4 //This is invalid, shouldn't be accessed.
         };
 
-        private struct Message
+        private readonly struct Message
         {
             public ulong Address  { get; }
             public ulong Size     { get; }
@@ -45,7 +45,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Ipc
                 request.CustomCmdBuffSize) { }
         }
 
-        private struct MessageHeader
+        private readonly struct MessageHeader
         {
             public uint Word0 { get; }
             public uint Word1 { get; }

Ryujinx.HLE/HOS/Kernel/Process/ProcessCreationInfo.cs

@@ -1,6 +1,6 @@
 namespace Ryujinx.HLE.HOS.Kernel.Process
 {
-    struct ProcessCreationInfo
+    readonly struct ProcessCreationInfo
     {
         public string Name { get; }
 

Ryujinx.HLE/HOS/ModLoader.cs

@@ -36,7 +36,7 @@ namespace Ryujinx.HLE.HOS
         private const string AmsNroPatchDir = "nro_patches";
         private const string AmsKipPatchDir = "kip_patches";
 
-        public struct Mod<T> where T : FileSystemInfo
+        public readonly struct Mod<T> where T : FileSystemInfo
         {
             public readonly string Name;
             public readonly T Path;

Ryujinx.HLE/HOS/Services/Account/Acc/Types/UserId.cs

@@ -7,7 +7,7 @@ using System.Runtime.InteropServices;
 namespace Ryujinx.HLE.HOS.Services.Account.Acc
 {
     [StructLayout(LayoutKind.Sequential)]
-    public struct UserId : IEquatable<UserId>
+    public readonly record struct UserId
     {
         public readonly long High;
         public readonly long Low;
@@ -50,37 +50,12 @@ namespace Ryujinx.HLE.HOS.Services.Account.Acc
             return High.ToString("x16") + Low.ToString("x16");
         }
 
-        public static bool operator ==(UserId x, UserId y)
-        {
-            return x.Equals(y);
-        }
-
-        public static bool operator !=(UserId x, UserId y)
-        {
-            return !x.Equals(y);
-        }
-
-        public override bool Equals(object obj)
-        {
-            return obj is UserId userId && Equals(userId);
-        }
-
-        public bool Equals(UserId cmpObj)
-        {
-            return Low == cmpObj.Low && High == cmpObj.High;
-        }
-
-        public override int GetHashCode()
-        {
-            return HashCode.Combine(Low, High);
-        }
-
-        public readonly Uid ToLibHacUid()
+        public Uid ToLibHacUid()
         {
             return new Uid((ulong)High, (ulong)Low);
         }
 
-        public readonly UInt128 ToUInt128()
+        public UInt128 ToUInt128()
         {
             return new UInt128((ulong)High, (ulong)Low);
         }

Ryujinx.HLE/HOS/Services/Nv/NvDrvServices/NvHostAsGpu/NvHostAsGpuDeviceFile.cs

@@ -20,7 +20,7 @@ namespace Ryujinx.HLE.HOS.Services.Nv.NvDrvServices.NvHostAsGpu
         private const ulong SmallRegionLimit = 0x400000000UL; // 16 GiB
         private const ulong DefaultUserSize = 1UL << 37;
 
-        private struct VmRegion
+        private readonly struct VmRegion
         {
             public ulong Start { get; }
             public ulong Limit { get; }

Ryujinx.HLE/HOS/Tamper/OperationBlock.cs

@@ -3,7 +3,7 @@ using System.Collections.Generic;
 
 namespace Ryujinx.HLE.HOS.Tamper
 {
-    struct OperationBlock
+    readonly struct OperationBlock
     {
         public byte[] BaseInstruction { get; }
         public List<IOperation> Operations { get; }