Allow the `CardinalityShapeSimilarity` metric to work with composite keys

[npatki]

Problem Description

In sdv-dev/SDV#2778, we are allowing for composite keys to be specified in the metadata. Although SDV Community won't be able to model composite keys, SDV Enterprise will have this capability. Therefore, a user might have real and synthetic data with composite keys.

In this case, the CardinalityShapeSimilarity metric should be able to work with composite keys.

Expected behavior

This metric currently just takes in metadata and reports the cardinality shape similarity for each relationship in the breakdown. So this end-user API doesn't need to change.

from sdmetrics.multi_table import CardinalityShapeSimilarity

CardinalityShapeSimilarity.compute_breakdown(
    real_data={
      'user': real_user_table,
      'sessions': real_sessions_table,
      'transactions': real_transactions_table
    },
    synthetic_data={
      'users': synthetic_user_table,
      'sessions': real_sessions_table,
      'transactions': real_transactions_table
    },
    metadata=multi_table_metadata_dict
)

However internally, we should make sure that the metric is computed based on all the columns involved in a primary or foreign key.

Additional context

This is a blocker for supporting composite keys in the reports. See #835.