feat: Updates serialization to use MMF (considerable memory savings) (#1841)

### Summary
Updates the serialization strategy to use `MemoryMappedFile` instead of thick buffers. This has the benefit of being on-par with the current implementation (based on hardware/OS), however won't incur the double-memory issue.

> [!Important]
> **Developer Note**
> The `BinaryFileWriter` and `BinaryFileReader` has been removed in favor of `MemoryMapFileWriter` and `UnmanagedDataReader`

Projects/Server.Tests/Tests/Network/Packets/Outgoing/AccountPacketTests.cs

@@ -48,8 +48,6 @@ public class AccountPacketTests : IClassFixture<ServerFixture>
         }
 
         public DateTime Created { get; set; }
-        public long SavePosition { get; set; }
-        public BufferWriter SaveBuffer { get; set; }
         public Serial Serial { get; }
         public void Deserialize(IGenericReader reader) => throw new NotImplementedException();