fix: Improve Purview scan reliability with collection hierarchy compliance with automatic reparenting

[Saswato-Microsoft]

Purpose

This pull request improves the reliability and user experience of Purview scan automation by ensuring that scans are always created within the correct collection hierarchy, as required by Purview. The main changes include automatically detecting and reparents the deployment collection under the datasource's collection to prevent Scan_CollectionOutOfBound errors, updating documentation to clarify this behavior, and providing clearer troubleshooting steps.

Purview scan collection handling improvements:

• The scan script (trigger_purview_scan_for_fabric_workspace.ps1) now automatically checks if the deployment collection is under the datasource's collection, and if not, attempts to reparent it as a child collection. If reparenting fails, it falls back to using the datasource's collection to ensure scans succeed.
• The script includes improved logic to resolve the correct collection from environment variables or by querying the datasource directly, increasing robustness in various deployment scenarios.

Documentation updates:

• The post-deployment documentation (docs/post_deployment_steps.md) now explains that if a tenant-level Fabric datasource already exists under a different collection, the automation will reparent the deployment collection as needed, and that collections may appear nested in the Purview portal.
• Troubleshooting steps are updated to describe the new automatic reparenting behavior and provide guidance for handling Scan_CollectionOutOfBound errors, including manual steps if automation fails.

These changes make the Purview scan process more resilient and provide clearer guidance for users during and after deployment.

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

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