Boost 1.87 discussion update

[anarthal]

Following the introduction of the new stable APIs (SQL formatting, any_connection, connection_pool and with_diagnostics), the discussion needs to be re-written. Prepared statements are now less relevant, sections on connection establishment/reconnection need to be condensed, and the overview needs to introduce these topics early, not as a extension.

[anarthal]

This was incorrectly closed by GitHub.