Replace almost all pp.Combine() into pp.Regex()

[embar-]

Majority of pp.Combine() are replaced into pp.Regex() for optimization. Only this one line is not changed: https://github.com/Vanderhoof/PyDBML/blob/2bf015cf0d4a242339dad45095afec2c0efa197f/pydbml/definitions/enum.py#L56

This will contribute to https://github.com/Vanderhoof/PyDBML/issues/59 solving

Some metrics:

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