pgsql: Add test tracking WAL receiver shutdown for primary_conninfo upd

Add test tracking WAL receiver shutdown for primary_conninfo updates

The test introduced by this commit checks that a reload of
primary_conninfo leads to a WAL receiver restarted, by looking at the
request generated in the server logs. This is something for what there
was no coverage.

This has come up for a different patch, while discussing a regression
where a WAL receiver should not be stopped while waiting for a new
position to stream, like at the end of a timeline. In the case of the
other patch, we want to check that this log entry is not generated, but
if the error message is reworded the test would become silently broken.
The test of this commit ensures that we at least keep track the log
message format, for a supported scenario.

Extracted from a larger patch by the same author.

Author: Xuneng Zhou <xunengzhou(at)gmail(dot)com>
Discussion: https://postgr.es/m/aQKlC1v2_MXGV6_9@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c9e38a569c5fe8006a08f63ba6b63d8021704c53

Modified Files
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src/test/recovery/t/040_standby_failover_slots_sync.pl | 12 ++++++++++++
1 file changed, 12 insertions(+)