Apply react-server condition for pages api

[huozhi]

Apply react-server condition and related API checks for pages API.

if you're doing react SSR with renderToString in middleware it should be disallowed. Imaging it could send the rendered html code to client and you display it in browser. But it might require hydration so it can be broken.

Follow up for #57448 , same reason explained in #57448
Closes NEXT-1653

[ijjk]

Stats from current PR

Default Build

General

	vercel/next.js canary	vercel/next.js pages-api-react-server	Change
buildDuration	10.2s	10s	N/A
buildDurationCached	5.8s	6s	⚠️ +180ms
nodeModulesSize	175 MB	175 MB	N/A
nextStartRea..uration (ms)	421ms	420ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js pages-api-react-server	Change
199-HASH.js gzip	32.3 kB	32.4 kB	N/A
3f784ff6-HASH.js gzip	53.2 kB	53.2 kB	N/A
99.HASH.js gzip	182 B	182 B	✓
framework-HASH.js gzip	45.5 kB	45.5 kB	✓
main-app-HASH.js gzip	254 B	252 B	N/A
main-HASH.js gzip	35.3 kB	35.4 kB	N/A
webpack-HASH.js gzip	1.75 kB	1.75 kB	N/A
Overall change	45.7 kB	45.7 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js pages-api-react-server	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js pages-api-react-server	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	2.59 kB	2.59 kB	✓
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	4.38 kB	4.38 kB	N/A
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.67 kB	2.67 kB	N/A
routerDirect..HASH.js gzip	316 B	318 B	N/A
script-HASH.js gzip	385 B	384 B	N/A
withRouter-HASH.js gzip	319 B	319 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.99 kB	3.99 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js pages-api-react-server	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 pages-api-react-server	Change
index.html gzip	529 B	530 B	N/A
link.html gzip	541 B	542 B	N/A
withRouter.html gzip	523 B	523 B	✓
Overall change	523 B	523 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js pages-api-react-server	Change
edge-ssr.js gzip	96 kB	96 kB	✓
page.js gzip	140 kB	140 kB	N/A
Overall change	96 kB	96 kB	✓

Middleware size

	vercel/next.js canary	vercel/next.js pages-api-react-server	Change
middleware-b..fest.js gzip	624 B	621 B	N/A
middleware-r..fest.js gzip	150 B	151 B	N/A
middleware.js gzip	25.6 kB	25.6 kB	N/A
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	1.92 kB	1.92 kB	✓

Commit: 2ff6c67

[ijjk]

Tests Passed