fix(ingest/bigquery): improve profiler to support multiple partition columns

[acrylJonny]

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 41.04478% with 79 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c/datahub/ingestion/source/bigquery_v2/profiler.py	46.15%	56 Missing ⚠️
...ub/ingestion/source/bigquery_v2/bigquery_schema.py	24.13%	22 Missing ⚠️
...ngestion/source/bigquery_v2/bigquery_schema_gen.py	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
...ngestion/source/bigquery_v2/bigquery_schema_gen.py	79.50% <0.00%> (ø)
...ub/ingestion/source/bigquery_v2/bigquery_schema.py	64.56% <24.13%> (-2.75%)	⬇️
...c/datahub/ingestion/source/bigquery_v2/profiler.py	48.90% <46.15%> (-4.50%)	⬇️

... and 20 files with indirect coverage changes

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