Expose additional regexp functions

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

Once https://github.com/apache/datafusion/issues/11946 is complete, add these functions to the python wrapper

**Describe the solution you'd like**

Expose additional regexp functions in python.

- [ ] [regexp_count()](https://pgpedia.info/r/regexp_count.html)
- [ ] [regexp_instr()](https://pgpedia.info/r/regexp_instr.html)
- [ ] [regexp_matches()](https://pgpedia.info/r/regexp_matches.html)
- [ ] [regexp_split_to_array()](https://pgpedia.info/r/regexp_split_to_array.html)
- [ ] [regexp_split_to_table()](https://pgpedia.info/r/regexp_split_to_table.html)
- [ ] [regexp_substr()](https://pgpedia.info/r/regexp_substr.html)

**Describe alternatives you've considered**

You can work around these with existing functions.