pgsql: Doc: Add the steps for upgrading the logical replication cluster

Doc: Add the steps for upgrading the logical replication cluster.

Author: Vignesh C
Reviewed-by: Peter Smith, Amit Kapila, Hayato Kuroda, Bharath Rupireddy
Discussion: https://postgr.es/m/CALDaNm1_iDO6srWzntqTr0ZDVkk2whVhNKEWAvtgZBfSmuBeZQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7fdeaf5774d05245e82632e763665ff62db5598e

Modified Files
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doc/src/sgml/glossary.sgml            |  10 +
doc/src/sgml/logical-replication.sgml | 775 ++++++++++++++++++++++++++++++++++
doc/src/sgml/ref/pgupgrade.sgml       | 131 +-----
3 files changed, 793 insertions(+), 123 deletions(-)