Parallelize requirePage when loading components

[shuding]

We can potentially speed it up a little bit by using Promise.all here. This was raised by @devknoll in #29470 (review).

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
buildDuration	15.5s	16.1s	⚠️ +585ms
buildDurationCached	3.9s	4s	⚠️ +35ms
nodeModulesSize	181 MB	181 MB	⚠️ +57 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.686	3.693	⚠️ +0.01
/ avg req/sec	678.21	676.88	⚠️ -1.33
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.988	1.92	-0.07
/error-in-render avg req/sec	1257.29	1302.18	+44.89

Client Bundles (main, webpack, commons)

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
779.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	27 kB	27 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	70.8 kB	70.8 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
_app-HASH.js gzip	977 B	977 B	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	311 B	311 B	✓
css-HASH.js gzip	328 B	328 B	✓
dynamic-HASH.js gzip	2.67 kB	2.67 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	918 B	918 B	✓
image-HASH.js gzip	4.15 kB	4.15 kB	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	1.66 kB	1.66 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	13 kB	13 kB	✓

Client Build Manifests

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
_buildManifest.js gzip	494 B	494 B	✓
Overall change	494 B	494 B	✓

Rendered Page Sizes

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
index.html gzip	539 B	539 B	✓
link.html gzip	551 B	551 B	✓
withRouter.html gzip	533 B	533 B	✓
Overall change	1.62 kB	1.62 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
buildDuration	7.9s	8.1s	⚠️ +248ms
buildDurationCached	4s	3.8s	-217ms
nodeModulesSize	181 MB	181 MB	⚠️ +57 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.621	3.687	⚠️ +0.07
/ avg req/sec	690.45	678.06	⚠️ -12.39
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.901	1.935	⚠️ +0.03
/error-in-render avg req/sec	1315.13	1292.06	⚠️ -23.07

Client Bundles (main, webpack, commons)

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
675-HASH.js gzip	13.8 kB	13.8 kB	✓
770.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	50.7 kB	50.7 kB	✓
main-HASH.js gzip	34.9 kB	34.9 kB	✓
webpack-HASH.js gzip	1.64 kB	1.64 kB	✓
Overall change	101 kB	101 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
polyfills-a4..dd70.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
_app-HASH.js gzip	1.33 kB	1.33 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	315 B	315 B	✓
css-HASH.js gzip	331 B	331 B	✓
dynamic-HASH.js gzip	2.79 kB	2.79 kB	✓
head-HASH.js gzip	356 B	356 B	✓
hooks-HASH.js gzip	637 B	637 B	✓
image-HASH.js gzip	573 B	573 B	✓
index-HASH.js gzip	262 B	262 B	✓
link-HASH.js gzip	2.2 kB	2.2 kB	✓
routerDirect..HASH.js gzip	326 B	326 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	322 B	322 B	✓
bb14e60e810b..30f.css gzip	125 B	125 B	✓
Overall change	10.1 kB	10.1 kB	✓

Client Build Manifests

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
_buildManifest.js gzip	512 B	512 B	✓
Overall change	512 B	512 B	✓

Rendered Page Sizes

	vercel/next.js canary	shuding/next.js shu/fc7a	Change
index.html gzip	538 B	538 B	✓
link.html gzip	550 B	550 B	✓
withRouter.html gzip	531 B	531 B	✓
Overall change	1.62 kB	1.62 kB	✓

Commit: 8998e47