pgsql: Don't use_physical_tlist for an IOS with non-returnable columns.

Don't use_physical_tlist for an IOS with non-returnable columns.

createplan.c tries to save a runtime projection step by specifying
a scan plan node's output as being exactly the table's columns, or
index's columns in the case of an index-only scan, if there is not a
reason to do otherwise.  This logic did not previously pay attention
to whether an index's columns are returnable.  That worked, sort of
accidentally, until commit 9a3ddeb51 taught setrefs.c to reject plans
that try to read a non-returnable column.  I have no desire to loosen
setrefs.c's new check, so instead adjust use_physical_tlist() to not
try to optimize this way when there are non-returnable column(s).

Per report from Ryan Kelly.  Like the previous patch, back-patch
to all supported branches.

Discussion: https://postgr.es/m/CAHUie24ddN+pDNw7fkhNrjrwAX=fXXfGZZEHhRuofV_N_ftaSg@mail.gmail.com

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/277e744ae176ef8e411a9e6c5b2e649322ee6bdd

Modified Files
--------------
src/backend/optimizer/plan/createplan.c | 16 ++++++++++++++++
src/test/regress/expected/gist.out      | 16 ++++++++++++++++
src/test/regress/sql/gist.sql           |  5 +++++
3 files changed, 37 insertions(+)