LP#1841974: Allow adjusted proximity for age-protect

LP#1841974: Allow adjusted proximity for age-protect

When testing prospective transit distance for age-protected items at
hold placement time we currently use the direct, baseline proximity
between the item circ (or owning) lib and the pickup lib.  With this
commit, setting a new YAOUS will allow the circ library of the item to
specify that a potentially-adjusted, calculated proximity should be used
instead.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Diane Disbro <ddisbro@scenicregional.org>
Signed-off-by: Nelson Appell <nappell@washmo.gov>
Signed-off-by: Jason Boyer <JBoyer@equinoxinitiative.org>