Remove v4.4 FCV handling for namespace length

NamespaceString::checkLengthForFCV returns true if the namespace length is valid for the FCV setting added in SERVER-41745. Need to clean up the callers of checkLengthForFCV, too.

Looks like jstests/multiVersion/long_collection_names.js can be removed.

Please check the SERVER ticket(s) that added the FCV gates for anything else incidental to remove, particularly any testing that can be deleted.