[ORC][ORC-RT] Add SimplePackedSerialization support for optionals.

This allows optionals to be serialized and deserialized, and used as arguments
and return values in SPS wrapper functions.

Serialization of optional values is indicated by use of the SPSOptional tag.
SPSOptionals are serialized serialized as a bool (false for no value, true for
value) plus the serialization of the contained value if any. Serialization
to/from std::optional is included in this commit.

This commit includes updates to SimplePackedSerialization in both ORC and the
ORC runtime.

, std::optional serialization.