Add ParseInt udf

[bealsbe]

Description

The goal of this PR is to add a new ParseInt UDF to the sml rules language. The UDF converts a numeric string to an integer.

Example sml:

  Result: int = ParseInt(s="42")                                                                                                                                                                                   
  # 42                                                                                                                                                                                                             
                                                                                                                                                                                                                   
  Result: int = ParseInt(s="-7")
  # -7                                                                                                                                                                                                             
                  
  Result: int = ParseInt(s="ABC")
  # None     
  

note: I wasn't too sure on what category to put this udf into. I am open to feedback to change the name.

Checklist

• Tests pass locally
• uv run ruff check . passes (no unused imports or other lint errors)
• uv tool run fawltydeps --check-unused --pyenv .venv passes (no unused dependencies)