Refactor memory managers to a common base class, consolidate Read() method logic (#6360)

* - add new abstract class `VirtualMemoryManagerBase`
- rename `MemoryManagerBase` to `VirtualMemoryManagerRefCountedBase` and derive from `VirtualMemoryManagerBase`
- change `AddressSpaceManager`, `HvMemoryManager`, `MemoryManager`, and `MemoryManagerHostMapped` to implement abstract members and use the inherited `void VirtualMemoryManagerBase.Read(TVirtual va, Span<byte> data)` implementation.

* move property `AddressSpaceSize` up by the other properties

src/Ryujinx.Cpu/VirtualMemoryManagerRefCountedBase.cs

@@ -0,0 +1,35 @@
+using Ryujinx.Memory;
+using System.Diagnostics;
+using System.Numerics;
+using System.Threading;
+
+namespace Ryujinx.Cpu
+{
+    public abstract class VirtualMemoryManagerRefCountedBase<TVirtual, TPhysical> : VirtualMemoryManagerBase<TVirtual, TPhysical>, IRefCounted
+        where TVirtual : IBinaryInteger<TVirtual>
+        where TPhysical : IBinaryInteger<TPhysical>
+    {
+        private int _referenceCount;
+
+        public void IncrementReferenceCount()
+        {
+            int newRefCount = Interlocked.Increment(ref _referenceCount);
+
+            Debug.Assert(newRefCount >= 1);
+        }
+
+        public void DecrementReferenceCount()
+        {
+            int newRefCount = Interlocked.Decrement(ref _referenceCount);
+
+            Debug.Assert(newRefCount >= 0);
+
+            if (newRefCount == 0)
+            {
+                Destroy();
+            }
+        }
+
+        protected abstract void Destroy();
+    }
+}