Add Serializable support for LurchTable<TKey, TValue>

[NightOwl888]

LurchTable<TKey, TValue> was not made serializable, however all of the other J2N collections are. Given the fact that we already have examples of dictionaries being serialized, this should be fairly straightforward to do. However, there may be additional state on LurchTable that needs to be handled that isn't part of other dictionaries in this library, so it needs analysis.

[NightOwl888]

Since serialization is obsolete in .NET 8, this is no longer necessary.