feat(sdk): add ContainerKey.parent_key method

[hsheth2]

This will be useful as we try to make our SDKs easier to use.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...adata-ingestion/src/datahub/emitter/mcp_builder.py	87.50%	1 Missing ⚠️

Files with missing lines	Coverage Δ
...adata-ingestion/src/datahub/emitter/mcp_builder.py	98.24% <87.50%> (-0.82%)	⬇️

... and 9 files with indirect coverage changes

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[sgomezvillamor]

LGTM
However, I'm curious, what's the use case? when I would need to generate the parent key for a given key? 🤔

[hsheth2]

@sgomezvillamor this is setting up some infra for the sdk improvements. Basically if we can infer the parent container, then we can also infer the browse path v2 automatically. That will let us avoid needing the auto_browse_path_v2 helper for basic sdk usages.