YT-380: Use Batch Processing in gitlab_backup.py
Currently, gitlab-backup.py processes all projects in the requested backup group simultaneously. When there are a large number of subgroups and projects, this results in high load on the GitLab instance, leading to performance degradation.
Added possibility to process by chanks (batch-es). This should reduce load in gitlab server during backup process.
Edited by Andrii Sosiuk