add unicode censored regex, string tokenizer udfs

[haileyok]

Adding two new string UDFs:

• StringTokenize, which converts the given text into a list of individual tokens (split at whitespace or punctuation). Not strictly necessary for this PR, but useful for it and feels like a good time to add it in
• CheckCensored, which builds a regex for a given input phrase then checks a given input token against the regex

There's some existing functionality for lookalikes in string.py, specifically the StringClean UDF. There's a variety of additional things that I've added in this new UDF though (that have also come up quite a bit in the wild)

• Still will match terms that attempt to obfuscate with "separator" characters, i.e. using "c___a___t" to try and get around matching for "cat"
• Handles zero-width spaces that are often used for the same purpose
• Handles a larger list of characters
• Allows for matching only when a given term is obfuscated, i.e. it's fine to use "cat" but not okay to use "<4t"

There's likely some additional overhead from using regex for this, but imo the additional flexibility/matching is worth that and the overhead is likely not too extreme, particularly since we're only compiling once per token+config combo anyway.