refactor: redefine configuration structure for all Database Lab products (database-lab#278)

Description

To standardize configuration file names and store metadata, redefine configuration structure for all Database Lab products

Related issue

database-lab#278 (closed)

Examples

Host machine

 ~/.dblab/
    joe/
      configs/
        - joe.yml
      meta/
        - sessions.json

Mounting

  --volume ~/.dblab/joe/configs:/home/configs:ro
  --volume ~/.dblab/joe/meta:/home/meta

Inside a Joe container

 /home/
     configs/
       - joe.yml
     meta/
       - sessions.json
     explain/
       - explain.yaml

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes and they have been reviewed OR there are no API changes