Implement a new JIT for Arm devices

src/Ryujinx.Cpu/LightningJit/CodeWriter.cs

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+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Cpu.LightningJit
+{
+    class CodeWriter
+    {
+        private readonly List<uint> _instructions;
+
+        public int InstructionPointer => _instructions.Count;
+
+        public CodeWriter()
+        {
+            _instructions = new();
+        }
+
+        public void WriteInstruction(uint instruction)
+        {
+            _instructions.Add(instruction);
+        }
+
+        public void WriteInstructionAt(int index, uint instruction)
+        {
+            _instructions[index] = instruction;
+        }
+
+        public void WriteInstructionsAt(int index, CodeWriter writer)
+        {
+            _instructions.InsertRange(index, writer._instructions);
+        }
+
+        public uint ReadInstructionAt(int index)
+        {
+            return _instructions[index];
+        }
+
+        public List<uint> GetList()
+        {
+            return _instructions;
+        }
+
+        public void RemoveLastInstruction()
+        {
+            if (_instructions.Count > 0)
+            {
+                _instructions.RemoveAt(_instructions.Count - 1);
+            }
+        }
+
+        public ReadOnlySpan<uint> AsSpan()
+        {
+            return CollectionsMarshal.AsSpan(_instructions);
+        }
+
+        public ReadOnlySpan<byte> AsByteSpan()
+        {
+            return MemoryMarshal.Cast<uint, byte>(AsSpan());
+        }
+    }
+}