[Antora] [PGSQL] Add Operate section to postgresql doc

[Arsnael]

Add the Operate section to the postgresql doc, similar to distributed here: https://james.staged.apache.org/james-distributed-app/3.8.1/operate/index.html

Refactor the distributed Operate section with the followings:

• Operator guide => can partial except Solving cassandra inconsistencies, Setting Cassandra user permissions, Cassandra table level configuration and Updating Cassandra schema version sections
• Performance checklist => can partial except Database setup and Cassandra section
• Logging => partials
• webadmin => partials except some cassandra specific sections and be careful of healthcheck too, some components differ
• Metrics => partials
• Migrating existing data => partials
• Command Line Interface => partials
• Security checklist => partials

Of course the cassandra sections in distributed doc should be replaced by postgres exclusive doc for pg doc.

Make sure the distributed doc is still the same after refactoring.

[vttranlina]

pr https://github.com/apache/james-project/pull/2326