pgsql: psql: Add tests for repeated calls of \bind[_named]

psql: Add tests for repeated calls of \bind[_named]

The implementation assumes that on multiple calls of these meta-commands
the last one wins.  Multiple \g calls in-between mean multiple
executions.

There were no tests to check these properties, hence let's add
something.

Author: Jelte Fennema-Nio, Michael Paquier
Discussion: https://postgr.es/m/CAGECzQSTE7CoM=Gst56Xj8pOvjaPr09+7jjtWqTC40pGETyAuA@mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/91287b5f5da324ac24678f556962e1b95e52240c

Modified Files
--------------
src/test/regress/expected/psql.out | 38 ++++++++++++++++++++++++++++++++++++++
src/test/regress/sql/psql.sql      |  9 +++++++++
2 files changed, 47 insertions(+)