fix(engine): PostgreSQL clean shutdown (#350)

Description

Implement a general approach to gracefully shutting down Postgres containers (both logical and physical).:

1. Execute the checkpoint command ("Run checkpoint command", commandCheckpoint)
2. Make sure that PostgreSQL stops using pg_ctl stop before stopping the container (func StopPostgres)
3. Then, stop the docker container.

Related issue

#350 (closed)

Examples

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have text changes OR there are text changes and they have been reviewed
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed
• MR does NOT have UI changes OR there are UI changes and they have been reviewed

Closes #350 (closed)