fix(core): Updates slice with range selectors (#583)

- [X] Replaces Span slicing with range selection
- [X] Replaces string slicing with range selection

Projects/Server/Serialization/BufferReader.cs

@@ -89,7 +89,7 @@ namespace Server
 
             int index = buffer.IndexOfTerminator(sizeT);
 
-            var span = buffer.SliceToLength(index < 0 ? size : index);
+            var span = buffer[..(index < 0 ? size : index)];
             _position += isFixedLength || index < 0 ? size : index + sizeT;
             return TextEncoding.GetString(span, encoding, safeString);
         }

Projects/Server/Serialization/BufferWriter.cs

@@ -225,7 +225,7 @@ namespace Server
             Span<byte> stack = stackalloc byte[16];
             value.TryWriteBytes(stack, out var bytesWritten);
             Write((byte)bytesWritten);
-            Write(stack.SliceToLength(bytesWritten));
+            Write(stack[..bytesWritten]);
         }
 
         public void Write(TimeSpan value)
@@ -441,7 +441,7 @@ namespace Server
                 charsLeft -= charCount;
                 current += charCount;
 
-                Write(span.SliceToLength(bytesWritten));
+                Write(span[..bytesWritten]);
             }
         }
     }