Use pooled memory and avoid memory copies (#6691)

* perf: use ByteMemoryPool

* feat: KPageTableBase/KPageTable new methods to read and write `ReadOnlySequence<byte>`

* new: add IWritableBlock.Write(ulong, ReadOnlySequence<byte>) with default impl

* perf: use GetReadOnlySequence() instead of GetSpan()

* perf: make `Parcel` IDisposable, use `ByteMemoryPool` for internal allocation, and make Parcel consumers dispose of it

* remove comment about copySize

* remove unnecessary Clear()

src/Ryujinx.HLE/HOS/Kernel/Memory/KPageTable.cs

@@ -2,6 +2,7 @@ using Ryujinx.Horizon.Common;
 using Ryujinx.Memory;
 using Ryujinx.Memory.Range;
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
 
@@ -34,6 +35,12 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             }
         }
 
+        /// <inheritdoc/>
+        protected override ReadOnlySequence<byte> GetReadOnlySequence(ulong va, int size)
+        {
+            return _cpuMemory.GetReadOnlySequence(va, size);
+        }
+
         /// <inheritdoc/>
         protected override ReadOnlySpan<byte> GetSpan(ulong va, int size)
         {
@@ -247,6 +254,12 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             _cpuMemory.SignalMemoryTracking(va, size, write);
         }
 
+        /// <inheritdoc/>
+        protected override void Write(ulong va, ReadOnlySequence<byte> data)
+        {
+            _cpuMemory.Write(va, data);
+        }
+
         /// <inheritdoc/>
         protected override void Write(ulong va, ReadOnlySpan<byte> data)
         {