Remove durable_rename_excl()
A previous commit replaced all the calls to this function with
durable_rename() as of
dac1ff3, making it used nowhere in the tree.
Using it in extension code is also risky based on the issues described
in this previous commit, so let's remove it. This makes possible the
removal of HAVE_WORKING_LINK.
Author: Nathan Bossart
Reviewed-by: Robert Haas, Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/
20220407182954.GA1231544@nathanxps13