pgsql: Add test for pg_restore_extended_stats() with multiranges

Add test for pg_restore_extended_stats() with multiranges

The restore of extended statistics has some paths dedicated to
multirange types and expressions for all the stats kinds supported, and
we did not have coverage for the case where an extended stats object
uses a multirange attribute with or without an expression.

Extracted from a larger patch by the same author, with a couple of
tweaks from me regarding the format of the output generated, to make it
more readable to the eye.

Author: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://postgr.es/m/CADkLM=dpz3KFnqP-dgJ-zvRvtjsa8UZv8wDAQdqho=qN3kX0Zg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0b7beec42ae2924f94410bded81f75f6f4eadd34

Modified Files
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src/test/regress/expected/stats_import.out | 62 ++++++++++++++++++++++++++++++
src/test/regress/sql/stats_import.sql | 41 ++++++++++++++++++++
2 files changed, 103 insertions(+)