pgsql: Doc: add a summary table to the CREATE POLICY docs.

Doc: add a summary table to the CREATE POLICY docs.

This table summarizes which RLS policy expressions apply to each
command type, and whether they apply to the old or new tuples (or
both), which saves reading through a lot of text.

Rod Taylor, hacked on by me. Reviewed by Fabien Coelho.

Discussion: https://postgr.es/m/CAHz80e4HxJShm6m9ZWFrHW=pgd2KP=RZmfFnEccujtPMiAOW5Q@mail.gmail.com

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a5339ac09502158d1c2b9503d077ad9a7114d620

Modified Files
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doc/src/sgml/ref/create_policy.sgml | 104 +++++++++++++++++++++++++++++++++++-
1 file changed, 103 insertions(+), 1 deletion(-)