pgsql: Add tests for pg_stat_io

Add tests for pg_stat_io

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: /messages/by-id/20200124195226.lth52iydq2n2uilq@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/10a082bf72150f49c34fcf152565c77d80f31a9c

Modified Files
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contrib/amcheck/expected/check_heap.out | 34 +++++
contrib/amcheck/sql/check_heap.sql | 27 ++++
src/test/regress/expected/stats.out | 228 ++++++++++++++++++++++++++++++++
src/test/regress/sql/stats.sql | 142 ++++++++++++++++++++
4 files changed, 431 insertions(+)