Skip regrouping on already regrouped manifests

[narekhovhannisyan]

Types of changes

• Enhancement (project structure, spelling, grammar, formatting)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

A description of the changes proposed in the Pull Request

• Optimize regroup to not run over already regrouped manifest.