-ensure we maintain the virtual override of InviteSession::provideOffer by moving the new 
 bool sendOfferAtAccept parameter (added in UAS PRACK changes) to two new methods
 -some apps relied on the virtualness of provideOffer to call the correct version

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@11167 ddefafc4-47db-0310-ae44-fa13212b10f2