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

Description

To standardize configuration file names and store metadata:

• redefine configuration structure for all Database Lab products
• adjust Docker images of Database Lab Engine and CI Checker
• remove old Docker images

Related issue

#278 (closed)

Examples

Host machine:

 ~/.dblab/
    cli/
     - cli.yml

    engine/
      configs/
        - server.yml
      meta/
        - state.json

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

    ci_checker/
      configs/
        - ci_checker.yml

Mounting

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

Inside a DLE container

 /home/
   dblab/
     configs/
       - server.yml
     meta/
       <metadata file1>
       <metadata file2>
     standard/
       postgres/
         default/
           10/
             ...
           11/
             ...
           12/
             ...
           13/
             pg_hba.conf
             postgresql.dblab.postgresql.conf
         control/
           pg_hba.conf
           postgresql.conf

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, specifications reflect those changes and they have been reviewed OR there are no API changes

Closes #278 (closed)