[REF] Extract portion of GroupContact load that builds the temporary table

[REF] Extract portion of GroupContact load that builds the temporary table

This is mostly a straight extraction. I chose to pass groupIDs in as an array
as I think that creates greater flexibility and I chose to pass CRM_Utils_SQL_TempTable
in rather than load it in the function because I have some ideas I'm working through
about how that might also provide more flexibilty

Those things can be changed later if we want as it IS a protected function