pgsql: Add option to specify timeout seconds to BackgroundPsql.pm.

Add option to specify timeout seconds to BackgroundPsql.pm.

Previously, a background psql session uses the default timeout and it
cannot be overridden. This change adds a new option to set the timeout
during start.

There are no users of this new option. It is needed for an upcoming
patch adding tests for XID wraparound.

Reviewed-by: Daniel Gustafsson, Noah Misch
Discussion: https://postgr.es/m/C9CF2F76-0D81-4C9D-9832-202BE8517056%40yesql.se

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/334f512f45ebc946ca1a5aa51808b4447f6384a0

Modified Files
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src/test/perl/PostgreSQL/Test/BackgroundPsql.pm | 10 ++++++----
src/test/perl/PostgreSQL/Test/Cluster.pm        | 11 ++++++++---
2 files changed, 14 insertions(+), 7 deletions(-)