Used SWC instead of Babel for Jest tests

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing issue: fixes Use SWC instead of Babel #1366
• That issue was marked as status: accepting prs

Overview

Uses @swc/jest instead of babel-jest.

• Execution: jest --clearCache before each command. Terminal was in focus and no actions taken on open programs during test runs.
• Hardware: Surface Laptop 4, 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz.
• Reporting: Time ranges are rounded numbers from 7 runs with the highest and lowest values removed.
• Software: WSL 2.0 in an Ubuntu drive via a VS Code terminal.

Command	Babel Time	SWC Time	(old - new) / old x 100%
jest	18-20 seconds	11-14 seconds	30-40% faster
jest --coverage --maxWorkers=2	23-28 seconds	20-25 seconds	10-13% faster

Sorted raw time data:

• Babel:
  • jest: 16.151, 17.686, 18.548, 18.738, 19.278, 19.676, 20.091
  • jest --coverage --maxWorkers=2: 22.320, 23.239, 24.898, 25.109, 27.087, 27.724, 28.649
• SWC:
  • jest: 11.488, 11.862, 12.709, 13.558, 13.932, 14.215, 14.351
  • jest --coverage --maxWorkers=2: 19.839, 20.708, 22.430, 23.670, 24.704, 25.013, 25.248

[JoshuaKGoldberg]

#1370 mentioned that @swc/core should be added too.

[JoshuaKGoldberg]

#1372

[JoshuaKGoldberg]

As of swc-project/jest#75, these are no longer required.

Suggested change

	{
	jsc: {
	target: "es2021",
	},
	},