[TextField] Revert #6143 and make expecting onBlur event arg optional

[chloerice]

WHY are these changes introduced?

#6143 exposed the event being passed into onBlur but didn't make expecting onBlur to be called with the event. That PR also took away the optionality of the expecting onFocus to be called with the event. Both of these changes cause type errors upstream in consuming TypeScript apps, making 9.17.0 an unsafe release.

WHAT is this pull request doing?

This PR reverts #6143 and makes the expecting onBlur to be called with the event optional.

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 in web with snapshot
• 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	196.83 KB (0%)
polaris-react-esm	132.14 KB (0%)
polaris-react-esnext	187.8 KB (0%)
polaris-react-css	42.16 KB (0%)

[chloerice]

/snapit

[github-actions]

🫰✨ Thanks @chloerice! Your snapshot has been published to npm.

Test the snapshot by updating your package.json with the newly published version:

yarn add @shopify/polaris@0.0.0-snapshot-release-20220617103156