Replace NodeJS v12 with NodeJS v16

[KengoTODA]

This action uses NodeJS v12 (Erbium) for now, which will end its support next April.

According to actions/runner#772 now GitHub Actions can run on NodeJS v16 (Gallium). So this PR suggests migrating to NodeJS v16. It also contains several related changes:

• Apply the recommended TSConfig settings for NodeJS v16
• Bump up TypeScript to target "ES2021"
• Bump up ESLint family to support NodeJS 16 and latest TypeScript
• Change error handling because the latest TypeScript treats caught object as unknown instead of any

Note that this action has already run its test on NodeJS v16 from this Dec/10th. So I believe that the feature won't be broken by this NodeJS upgrade.

Thanks for checking my PR! 👋

[JLLeitschuh]

@KengoTODA Thank you very much for your contribution here! Your PR actually inspired me to add some additional checks to our pipeline. Your contribution includes quite a few changes that are difficult to review as the changes are made to generated code. As such, I introduced an additional CI check to verify your changes and the generated code line-up.

https://github.com/gradle/wrapper-validation-action/blob/master/.github/workflows/check-dist.yml

Could you do me a favor and rebase your changes so those new checks are executed? 😃

[JLLeitschuh]

Also, you'll probably need to update this after rebasing:

wrapper-validation-action/.github/workflows/check-dist.yml

Lines 27 to 30 in 781fa15

	- name: Set Node.js 12.x
	uses: actions/[email protected]
	with:
	node-version: 12.x

[JLLeitschuh]

Much appreciated. LGTM!