[Draft] Node grouping

[ankatiyar]

Description

Draft PR to demo - #4376

Development notes

Add attributes to pipeline to get dependencies and node grouped by namespace. (The property names just for the prototype)
This PR offers a version of the information from the group_by_namespace() method added in kedro-airflow in kedro-org/kedro-plugins#981

Questions to be considered:

• Does it make sense to have this API in the Pipeline class?
• The plugins would still have to discern whether they're executing a node or a group of nodes i.e would have to pick kedro run --node=<nodename> or kedro run --namespace=<namespace> for each "task". How do we make this easier?

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Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team