ResultCache impl for extensions of DataConnector

[Cantor, Scott]

> Actually AbstractDataConnector was moved out of impl in a recent release.

That was, but not the search connector base class. All the shared code for LDAP/JDBC is impl. I thought the cache handling was in that layer, not the top. Might be mistaken there.

> I'd be interested in any suggestions of classes to move oout from API,
> possible as part of IDP-1179.  We know that we started of
> quite conservatively with API classes during V3, but now we have more
> experiences we can make changes.

I was planning to punt it to V4 but we can talk about it.

-- Scott