Support absolute expiration of server side sessions when CoordinateLifetimeWithUserSession is enabled

[josephdecock]

ISessionCoordinationService.ValidateSessionAsync always extends the server-side session. We call this method when validating refresh and reference tokens. The implication is that in order to use refresh (or reference tokens) with server-side sessions with an absolute expiration, the user must customize the ValidateSessionAsync method.

See also https://github.com/DuendeSoftware/Support/issues/1057