Fix unique key generation

[fealho]

The _make_ids function in sdv/metadata/table.py fails to generate high numbers of unique values.

SDV/sdv/metadata/table.py

Line 521 in 4d08911

def _make_ids(self, name, field_metadata, length):

Error message: ValueError: Unable to generate 1519994 unique values for field drug regex "[a-z][A-Z]+"

Changes

The _make_ids function should be adapted to use the strings_from_regex function from module sdv/metadata/utils.py
The total number requested IDs should be checked against the size returned by the strings_from_regex function and a ValueError should be raised if too many values are requested
The default regex should be changed from [a-z][A-Z]+ to [a-zA-Z]+