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: https://postgr.es/m/Zab9GiV63EENDcWG@momjian.us

Co-authored-by: David G. Johnston

Backpatch-through: 16

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/88be3f076c4cc26d31586d433cb41185eebb3c11

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(-)