pgsql: Add regression test for recovery pause.

Add regression test for recovery pause.

Previously there was no regression test for recovery pause feature.
This commit adds the test that checks

- recovery can be paused or resumed expectedly
- pg_get_wal_replay_pause_state() reports the correct pause state
- the paused state ends and promotion continues if a promotion
   is triggered while recovery is paused

Suggested-by: Michael Paquier
Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Dilip Kumar
Discussion: https://postgr.es/m/YKNirzqM1HYyk5h4@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6bbc5c5e96b08f6b8c7d28d10ed8dfe6c49dca30

Modified Files
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src/test/recovery/t/005_replay_delay.pl | 59 +++++++++++++++++++++++++++++++--
1 file changed, 57 insertions(+), 2 deletions(-)