[Data Synchronization/Matching] Delegate to Spark for checking existence of columns in the given dataframes

[rdsharma26]

Description of changes:

• Prior to this change, we were doing case sensitive equality checks of non-key columns.
• This makes the utility more restrictive, as Spark does not care about the casing of column names.
• With this change, we rely on Spark to check if a column exists in the given dataframe. If Spark can find the column, we can proceed with the rest of the check.

Issue #, if available: N/A

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