CSS-10465 update trino secret format

[AmberCharitos]

With the existing structure of the catalog-config.yaml file, this quickly becomes large enough that k8s secrets no longer support the size resulting in an error when adding additional catalogs. https://warthogs.atlassian.net/browse/CSS-10465

This PR:

• Updates the config file format to use a backend structure to prevent repetition when adding multiple databases from the same server.
• Adds logic to the charm code for reading this config and turning it into catalogs in trino.

Please note, for now this just supports the addition of postgresql connectors, in the future we can add additional backends and charm logic for other supported connectors but it is very hard to generalised for all as every connector differs considerably in configuration values.

[kelkawi-a]

LGTM