pgsql: pg_dump: avoid unsafe function calls in getPolicies().

pg_dump: avoid unsafe function calls in getPolicies().

getPolicies() had the same disease I fixed in other places in
commit e3fcbbd62, i.e., it was calling pg_get_expr() for
expressions on tables that we don't necessarily have lock on.
To fix, restrict the query to only collect interesting rows,
rather than doing the filtering on the client side.

Like the previous patch, apply to HEAD only for now.

Discussion: https://postgr.es/m/2273648.1634764485@sss.pgh.pa.us
Discussion: https://postgr.es/m/7d7eb6128f40401d81b3b7a898b6b4de@W2012-02.nidsa.loc

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3e6e86abca0138abd7265306beb6346dc2d9e221

Modified Files
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src/bin/pg_dump/pg_dump.c | 42 +++++++++++++++++++++++++++++-------------
1 file changed, 29 insertions(+), 13 deletions(-)