Add proper headers to responses in web server

[shuding]

This PR adds the X-Powered-By and Content-Type headers to responses sent by the web server. The latter enables compression for the Edge runtime. Still, the web server doesn't have Content-Length and ETag as the response is usually dynamic.

Part of #31506.

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

Feature

• Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• Integration tests added
• Documentation added
• Telemetry added. In case of a feature if it's used or not.
• Errors have helpful link attached, see contributing.md

Documentation / Examples

• Make sure the linting passes by running yarn lint

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	shuding/next.js shu/8644	Change
buildDuration	15.4s	15.5s	⚠️ +159ms
buildDurationCached	6.1s	6s	-88ms
nodeModulesSize	367 MB	367 MB	⚠️ +1.21 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	shuding/next.js shu/8644	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.925	2.94	⚠️ +0.02
/ avg req/sec	854.57	850.24	⚠️ -4.33
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.357	1.351	-0.01
/error-in-render avg req/sec	1842.51	1850.06	+7.55

Client Bundles (main, webpack)

	vercel/next.js canary	shuding/next.js shu/8644	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	27.8 kB	27.8 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.5 kB	71.5 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	shuding/next.js shu/8644	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	shuding/next.js shu/8644	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	326 B	326 B	✓
dynamic-HASH.js gzip	2.57 kB	2.57 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	919 B	919 B	✓
image-HASH.js gzip	5.05 kB	5.05 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.26 kB	2.26 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.7 kB	14.7 kB	✓

Client Build Manifests

	vercel/next.js canary	shuding/next.js shu/8644	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	shuding/next.js shu/8644	Change
index.html gzip	531 B	531 B	✓
link.html gzip	544 B	544 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	shuding/next.js shu/8644	Change
buildDuration	18.8s	18.9s	⚠️ +31ms
buildDurationCached	6.2s	6.2s	-71ms
nodeModulesSize	367 MB	367 MB	⚠️ +1.21 kB

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	shuding/next.js shu/8644	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.921	2.93	⚠️ +0.01
/ avg req/sec	855.98	853.2	⚠️ -2.78
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.335	1.351	⚠️ +0.02
/error-in-render avg req/sec	1872.6	1849.99	⚠️ -22.61

Client Bundles (main, webpack)

	vercel/next.js canary	shuding/next.js shu/8644	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.1 kB	42.1 kB	✓
main-HASH.js gzip	27.8 kB	27.8 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.6 kB	71.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	shuding/next.js shu/8644	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	shuding/next.js shu/8644	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.56 kB	2.56 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	911 B	911 B	✓
image-HASH.js gzip	5.08 kB	5.08 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.28 kB	2.28 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.7 kB	14.7 kB	✓

Client Build Manifests

	vercel/next.js canary	shuding/next.js shu/8644	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	shuding/next.js shu/8644	Change
index.html gzip	534 B	534 B	✓
link.html gzip	547 B	547 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.61 kB	1.61 kB	✓

Commit: cfb4362