Add Polaris migrator utility to getFunctionArgs

[aaronccasanova]

WHAT is this pull request doing?

This PR introduces a getFunctionArgs utility to the Polaris migrator. For examples of how this can be leveraged, see the replace-typography-declarations migration which uses getFunctionArgs to identify if a function was provided the expected number of args and uses the args to access replacement values.

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

Copy-paste this code in playground/Playground.tsx:

import React from 'react';
import {Page} from '../src';

export function Playground() {
  return (
    <Page title="Playground">
      {/* Add the code you want to test in here */}
    </Page>
  );
}

🎩 checklist

• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility
• Updated the component's README.md with documentation changes
• Tophatted documentation changes in the style guide

[lgriffee]

This is awesome! Really looking forward to using this new utility 🛳✨🎉

[chloerice]

🎉