pgsql: doc: improve role option documentation

doc: improve role option documentation

Role option management was changed in Postgres 16. This patch improves
the docs around these changes, including CREATE ROLE's INHERIT option,
inheritance handling, and grant's ability to change role options.

Discussion: /messages/by-id/Zab9GiV63EENDcWG@momjian.us

Co-authored-by: David G. Johnston

Backpatch-through: 16

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/21912e3c0262e2cfe64856e028799d6927862563

Modified Files
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doc/src/sgml/ref/create_role.sgml | 87 ++++++++++++++++++++++++---------------
doc/src/sgml/ref/grant.sgml | 29 +++++++------
doc/src/sgml/user-manag.sgml | 8 ++--
3 files changed, 74 insertions(+), 50 deletions(-)