fix: various issues related to the automated snapshot management and sync instance (#152)

Description

Fix auto snapshots:

• scheduler validation
• skip physical restore when PGDATA is not empty
• pre-snapshots: snapshots and clones management
• clean-up snapshot command
• improve console output

Related issue

#152 (closed)

Examples

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 #152 (closed)