Fix: support datetime + pandas.Timedelta addition in AddNumericScalar

[Hasan-8326]

This pull request fixes an issue where adding a pandas.Timedelta to a datetime feature (e.g., f + pd.Timedelta(1, 'y')) raised an AssertionError in Featuretools. The root cause was that the AddNumericScalar primitive only supported numeric addition and did not handle datetime + timedelta operations. This update enhances AddNumericScalar to support both numeric and datetime inputs, allowing datetime features to be correctly offset by pandas.Timedelta values. The change maintains backward compatibility with numeric features and ensures that time-based arithmetic works as expected in feature definitions.

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