pgsql: Add test with multirange type for pg_restore_attribute_stats()

Add test with multirange type for pg_restore_attribute_stats()

This commit adds a test for pg_restore_attribute_stats() with the
injection of statistics related to a multirange type. This case is
supported in statatt_get_type() since its introduction in ce207d2a7901,
but there was no test in the main regression test suite to check for the
case where attribute stats is restored for a multirange type, as done by
multirange_typanalyze().

Author: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
Discussion: https://postgr.es/m/CADkLM=c3JivzHNXLt-X_JicYknRYwLTiOCHOPiKagm2_vdrFUg@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/d4504d6f60e07516cd3b0311054e6f8e74496281

Modified Files
--------------
src/test/regress/expected/stats_import.out | 29 ++++++++++++++++++++++++++++-
src/test/regress/sql/stats_import.sql | 24 ++++++++++++++++++++++++
2 files changed, 52 insertions(+), 1 deletion(-)