pgsql: Fix missing installation rules for BackgroundPsql.pm

Fix missing installation rules for BackgroundPsql.pm

Commit 664d75753 added the BackgroundPsql module with helper functions
for tests running interactive or background psql tasks. The new module
was however not added to the install rules of the build systems.

Reported-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Discussion: /messages/by-id/c0ba3008-dbc8-e53f-29f2-2e9abe72b2a2@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a4c17c86176cfa712f541b81b2a026ae054b275e

Modified Files
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src/test/perl/Makefile | 1 +
src/test/perl/meson.build | 1 +
2 files changed, 2 insertions(+)