pgsql: Add a regression test for contrib/pg_prewarm.

Add a regression test for contrib/pg_prewarm.

We had a little bit of coverage here thanks to e2f65f425,
but not enough; notably, autoprewarm wasn't exercised at all.

Dong Wook Lee, with help from Julien Rouhaud and myself

Discussion: /messages/by-id/20220629053812.mifmdrch5iuasg2s@home-desktop

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2865b4060a434855f90fda41f1b8f4bca7c55b0e

Modified Files
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contrib/pg_prewarm/.gitignore | 4 +++
contrib/pg_prewarm/Makefile | 2 ++
contrib/pg_prewarm/t/001_basic.pl | 58 +++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+)