pgsql: Move SQL tests of pg_stat_io for WAL data to recovery test 029_s

Move SQL tests of pg_stat_io for WAL data to recovery test 029_stats_restart

Three tests in the main regression test suite are proving to not be
portable across multiple runs on a deployed cluster as stats of
pg_stat_io are reset.  Problems happen for tests on:
- Writes of WAL in the init context, when creating a WAL segment.
- Syncs of WAL in the init context, when creating a WAL segment.
- Reads of WAL in the normal context, requiring a WAL record to be read.
For a `make check`, this could rely on the checkpoint record read by the
startup process when starting the cluster, something that is not going
to work for a deployed node.

Two of the three tests are moved to the recovery TAP test
029_stats_restart, where we already check the consistency of stats
data.  The test for syncs is dropped as TAP can run with fsync=off.  The
other two are checked with some data from a freshly-initialized cluster.

Per discussion with Tom Lane, Bertrand Drouvot and Nazir Bilal Yavuz.

Discussion: https://postgr.es/m/915687.1738780322@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/428fadb7e97e3c95180d75dea73de99c491a9f65

Modified Files
--------------
src/test/recovery/t/029_stats_restart.pl | 34 +++++++++++++++++++++++++++++++-
src/test/regress/expected/stats.out      | 27 -------------------------
src/test/regress/sql/stats.sql           | 14 -------------
3 files changed, 33 insertions(+), 42 deletions(-)