Adding Integer.Parse

[jdunkerley]

Pull Request Description

Implementing Integer.Parse - based on Long.parseLong

Important Notes

• worth considering moving to builtins space but will do this as a later task
• speed benefits over Decimal.parse .floor - 138ms vs 86ms for 1mm parses

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH ./run dist and ./run watch.

[radeusgd]

Looks good, but I think as we are trying to have quite comprehensive tests, it may be worth adding a few more tests - mostly so that we can catch any regressions in the future.