Reduce usage of Marshal.PtrToStructure and Marshal.StructureToPtr (#3805)

* common: Make BinaryReaderExtensions Read & Write take unamanged types

This allows us to not rely on Marshal.PtrToStructure and Marshal.StructureToPtr for those.

* common: Make MemoryHelper Read & Write takes unamanged types

* Update Marshal.SizeOf => Unsafe.SizeOf when appropriate and start moving software applet to unmanaged types

Ryujinx.HLE/HOS/Applets/SoftwareKeyboard/SoftwareKeyboardDictSet.cs

@@ -1,4 +1,5 @@
-using System.Runtime.InteropServices;
+using Ryujinx.Common.Memory;
+using System.Runtime.InteropServices;
 
 namespace Ryujinx.HLE.HOS.Applets.SoftwareKeyboard
 {
@@ -21,8 +22,7 @@ namespace Ryujinx.HLE.HOS.Applets.SoftwareKeyboard
         /// <summary>
         /// Array of word entries in the buffer.
         /// </summary>
-        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 24)]
-        public ulong[] Entries;
+        public Array24<ulong> Entries;
 
         /// <summary>
         /// Number of used entries in the Entries field.