adds PathAggregation

[bwalsh]

Pull Request Overview

This PR adds a new PathAggregation feature that provides file count and size statistics grouped by directory paths from DocumentReference data.

• Introduces a new path aggregation module with utilities for normalizing paths and generating directory prefixes
• Adds a path_aggregation method to the dataframer that aggregates DocumentReference files by path
• Extends the CLI to support the new PathAggregation data type

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
gen3_tracker/meta/path_aggregation.py	New module with path normalization utilities and global aggregator state
gen3_tracker/meta/dataframer.py	Adds path_aggregation method and registers PathAggregation data type
gen3_tracker/meta/cli.py	Extends CLI choices to include PathAggregation option
tests/unit/dataframer/test_dataframer.py	Adds comprehensive test for path aggregation functionality

Motivation and Context

Provides path hierarchy

How Has This Been Tested?

See unit test

Types of Changes

• New feature (non-breaking change which adds functionality)

Checklist

• I have updated the documentation accordingly (link here).
• I have tested that this feature locally.
• I have added tests to cover my changes.
• All new and existing tests passed.
• Reviewer has tested this feature locally