[Box] Add support for overflowX, overflowY, and width props

[laurkim]

WHY are these changes introduced?

While rebuilding the Modal component with our layout primitives, I came across gaps that our layout components don't yet support. We have no way of handling content overflow and while we did ship a PR to add maxWidth support to Box, we should also support width.

WHAT is this pull request doing?

• Adds width prop
• Adds overflowX and overflowY with type definition limited to hidden or scroll after discussions with @sarahill
• Removes px from being interpolated in the maxWidth prop because these could be percentages

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

[github-actions]

size-limit report 📦

Path	Size
polaris-react-cjs	209.2 KB (+0.03% 🔺)
polaris-react-esm	135.66 KB (+0.04% 🔺)
polaris-react-esnext	191.05 KB (+0.05% 🔺)
polaris-react-css	41.55 KB (+0.11% 🔺)