pgsql: Add PostgreSQL::Test::Cluster::is_alive()

Add PostgreSQL::Test::Cluster::is_alive()

This new routine acts as a wrapper of pg_isready, that can be run on a
node to check its connection status.  This will be used in a recovery
test in a follow-up commit.

Suggested-by: Andres Freund <andres@anarazel.de>
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/CAN55FZ1D6KXvjSs7YGsDeadqCxNF3UUhjRAfforzzP0k-cE=bA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d4c9195eff419dcad47d5c2137e31f790c32adde

Modified Files
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src/test/perl/PostgreSQL/Test/Cluster.pm | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)