pgsql: doc: Improve pgoutput documentation.

doc: Improve pgoutput documentation.

This commit updates the pgoutput documentation with the following changes:

- Specify the data type for each pgoutput option.
- Clarify the relationship between proto_version and options such as
   streaming and two_phase.
- Add a note on the use of pg_logical_slot_peek_changes and
   pg_logical_slot_get_changes with pgoutput.

Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Discussion: https://postgr.es/m/CAHGQGwFJTbygdhhjR_iP4Oem=Lo1xsptWWOq825uoW+hG_Lfnw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/38c5fbd97ee6a8409c6c41d6af0c06169cd51c2b

Modified Files
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doc/src/sgml/func/func-admin.sgml |   2 +-
doc/src/sgml/logicaldecoding.sgml | 118 ++++++++++++++++++++++----------------
2 files changed, 69 insertions(+), 51 deletions(-)