fix: get the name of the latest WAL-G backup (#365)

Description

Implemented a workaround for identification of the "LATEST" backup from wal-g output:

• use wal-g backup-list / wal-g backup-list --detail to obtain the name of the latest backup
• identify the last backup through Init() function on restorer interface

Related issue

#365 (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 #365 (closed)