feat(DeltaUtils): UNIC-2021 Overload stat methods to accept a pre-computed statsDf

[laurabegin]

Summary

• Adds DataFrame overloads for all DeltaUtils stat methods that previously only accepted a path: String
• The path versions now delegate to the statsDf overloads, so callers that already have a snapshot from getTableStats can pass it directly and avoid re-reading the Delta log
• Affected methods: getPartitionValues, getNumRecords, getNumRecordsPerPartition, getMinValues, getMinValuesPerPartition, getMaxValues, getMaxValuesPerPartition, getNullCounts, getNullCountsPerPartition

Motivation

QA tests in unic-etl were calling getTableStats multiple times per dataset (once for a hasStats probe, then again inside each stat function). This caused redundant Delta log reads from Minio and a cascade of stuck Spark jobs. The new overloads allow callers to read the snapshot once and reuse it.

Test plan

• Existing DeltaUtilsSpec tests pass
• Verify the path overloads still behave identically (they delegate to the new statsDf overloads)

🤖 Generated with Claude Code

[AhmedSabsabi]

Looks like a solid refactor, but I want to double-check how these methods are used in unic-etl before approving, just to make sure nothing breaks downstream.

Good for me

[laurabegin]

@AhmedSabsabi FYI we use a pinned version in unic-etl so nothing will break by merging this. I will be able to deploy a new datalake-lib version, then update it in unic-etl and test the changes in unic-etl.