chore: drop undici

[balazsorban44]

What?

Note: This is not a breaking change, just removing some unused code.

Why?

Since #56896 we don't need this, as Node.js 18+ has fetch exposed by default.

How?

Depends on #56896, #56909

We already didn't load fetch if globalThis had it (ie. Node.js 18+ environments), and since we are dropping support for Node.js 16, these code paths should have no effect on runtime behavior.

See: https://nodejs.org/docs/latest-v18.x/api/globals.html#fetch

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build

General

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
buildDuration	10.4s	10.4s	N/A
buildDurationCached	6.1s	6s	N/A
nodeModulesSize	175 MB	174 MB	N/A
nextStartRea..uration (ms)	530ms	513ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
199-HASH.js gzip	27.5 kB	27.5 kB	N/A
3f784ff6-HASH.js gzip	53.3 kB	53.3 kB	✓
99.HASH.js gzip	182 B	182 B	✓
framework-HASH.js gzip	45.3 kB	45.3 kB	✓
main-app-HASH.js gzip	254 B	252 B	N/A
main-HASH.js gzip	32.9 kB	32.9 kB	N/A
webpack-HASH.js gzip	1.75 kB	1.75 kB	N/A
Overall change	98.8 kB	98.8 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
_app-HASH.js gzip	206 B	205 B	N/A
_error-HASH.js gzip	182 B	180 B	N/A
amp-HASH.js gzip	506 B	505 B	N/A
css-HASH.js gzip	322 B	323 B	N/A
dynamic-HASH.js gzip	2.57 kB	2.57 kB	N/A
edge-ssr-HASH.js gzip	260 B	259 B	N/A
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	369 B	369 B	✓
image-HASH.js gzip	4.36 kB	4.36 kB	N/A
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.64 kB	2.63 kB	N/A
routerDirect..HASH.js gzip	312 B	311 B	N/A
script-HASH.js gzip	385 B	384 B	N/A
withRouter-HASH.js gzip	307 B	308 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	1.08 kB	1.08 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
_buildManifest.js gzip	484 B	482 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
index.html gzip	529 B	529 B	✓
link.html gzip	544 B	542 B	N/A
withRouter.html gzip	524 B	523 B	N/A
Overall change	529 B	529 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
edge-ssr.js gzip	93.7 kB	93.7 kB	N/A
page.js gzip	155 kB	155 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js chore/drop-undici	Change
middleware-b..fest.js gzip	624 B	623 B	N/A
middleware-r..fest.js gzip	150 B	151 B	N/A
middleware.js gzip	22.5 kB	22.5 kB	N/A
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	1.92 kB	1.92 kB	✓

Commit: 0ff6487