Metadata.add_column can be slow

[amontanez24]

Problem Description

The metadata.add_column method can sometimes be unreasonably slow (a few seconds). This seems to be because during its validation, we check if it isn't a faker function, which seems to be a slow method in RDT. https://github.com/sdv-dev/SDV/blob/8cec1f7c49c4e4242c260653db8bea042ad9f209/sdv/metadata/single_table.py#L229-L243

Expected behavior

• See if the validation can be sped up. This may require speeding up the underlying function in RDT