Doc: Make logical replication examples executable in bulk.

Doc: Make logical replication examples executable in bulk.

To improve the usability of logical replication examples, we need to
enable bulk copy-pasting of DML/DDL series.

Currently, output command tags and prompts disrupt this workflow. While
prompts are typically removed, converting them to comments is acceptable
here, given the multi-server context.

Additionally, ensure all examples containing operators like < and > are
wrapped in CDATA blocks to guarantee correct rendering and consistency
with other places.

Author: David G. Johnston <[email protected]>
Reviewed-by: Peter Smith <[email protected]>
Discussion: https://postgr.es/m/CAKFQuwbhbL1uaDTuo9shmo1rA-fX6XGotR7qZQ7rd-ia5ZDoQA@mail.gmail.com