This is to create an instance of a Summary given a serialized representation.
The user may assume that the start of the given Memory is the correct place to start
deserializing. However, the user must be able to determine the number of bytes required to
deserialize the summary as the capacity of the given Memory may
include multiple such summaries and may be much larger than required for a single summary.
mem - Memory object with serialized representation of a Summary
DeserializedResult object, which contains a Summary object and number of bytes read
from the Memory