Bump babel target to Node.js 12

[styfle]

Next.js 11 supports Node.js 12 and newer. This PR updates babel to reflect this.

Follow up to PR #25761

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall decrease ✓

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
buildDuration	15.3s	15.6s	⚠️ +291ms
buildDurationCached	3.6s	3.5s	-39ms
nodeModulesSize	49.3 MB	49.3 MB	-4 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.482	2.476	-0.01
/ avg req/sec	1007.18	1009.57	+2.39
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.409	1.346	-0.06
/error-in-render avg req/sec	1774.78	1857.06	+82.28

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
359.HASH.js gzip	3.09 kB	3.09 kB	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	20.9 kB	20.9 kB	✓
webpack-HASH.js gzip	1.49 kB	1.49 kB	✓
Overall change	67.6 kB	67.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
polyfills-HASH.js gzip	31.1 kB	31.1 kB	✓
Overall change	31.1 kB	31.1 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
_app-HASH.js gzip	803 B	803 B	✓
_error-HASH.js gzip	3.18 kB	3.18 kB	✓
amp-HASH.js gzip	526 B	526 B	✓
css-HASH.js gzip	329 B	329 B	✓
hooks-HASH.js gzip	903 B	903 B	✓
image-HASH.js gzip	5.69 kB	5.69 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	1.66 kB	1.66 kB	✓
routerDirect..HASH.js gzip	319 B	319 B	✓
withRouter-HASH.js gzip	320 B	320 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	14.1 kB	14.1 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
_buildManifest.js gzip	419 B	419 B	✓
Overall change	419 B	419 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
index.html gzip	531 B	531 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	524 B	524 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Webpack 4 Mode (Decrease detected ✓)

General Overall decrease ✓

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
buildDuration	12.4s	12.5s	⚠️ +56ms
buildDurationCached	4.9s	4.8s	-148ms
nodeModulesSize	49.3 MB	49.3 MB	-4 kB

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.503	2.48	-0.02
/ avg req/sec	998.99	1007.97	+8.98
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.385	1.424	⚠️ +0.04
/error-in-render avg req/sec	1804.94	1755.85	⚠️ -49.09

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
14.HASH.js gzip	3.11 kB	3.11 kB	✓
677f882d2ed8..HASH.js gzip	13.9 kB	13.9 kB	✓
framework.HASH.js gzip	41.8 kB	41.8 kB	✓
main-HASH.js gzip	8.17 kB	8.17 kB	✓
webpack-HASH.js gzip	1.19 kB	1.19 kB	✓
Overall change	68.1 kB	68.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
polyfills-HASH.js gzip	31.3 kB	31.3 kB	✓
Overall change	31.3 kB	31.3 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
_app-HASH.js gzip	791 B	791 B	✓
_error-HASH.js gzip	3.83 kB	3.83 kB	✓
amp-HASH.js gzip	531 B	531 B	✓
css-HASH.js gzip	333 B	333 B	✓
hooks-HASH.js gzip	910 B	910 B	✓
index-HASH.js gzip	230 B	230 B	✓
link-HASH.js gzip	1.64 kB	1.64 kB	✓
routerDirect..HASH.js gzip	297 B	297 B	✓
withRouter-HASH.js gzip	293 B	293 B	✓
e025d2764813..52f.css gzip	125 B	125 B	✓
Overall change	8.98 kB	8.98 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
_buildManifest.js gzip	418 B	418 B	✓
Overall change	418 B	418 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js babel-target-node-12	Change
index.html gzip	574 B	574 B	✓
link.html gzip	585 B	585 B	✓
withRouter.html gzip	568 B	568 B	✓
Overall change	1.73 kB	1.73 kB	✓

Commit: 7f997f2