Support generating multi-meta tags for metadata api other prop

[huozhi]

Give flexibility to generate multiple same-key metadata k-v

export const metadata = {
  other: {
    'my-own-meta-name': ['1','2']
  }
}

Before

<meta key="my-own-meta-name" value="1,2">

Now

<meta key="my-own-meta-name" value="1">
<meta key="my-own-meta-name" value="2">

When you want to have the array joined like value, you can do it when you pass the value down to other property. And if you want multiple one, you could specify array to generate them

Closes #57051
Closes NEXT-1746

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
buildDuration	10.4s	10.5s	⚠️ +130ms
buildDurationCached	5.9s	6.5s	⚠️ +627ms
nodeModulesSize	199 MB	199 MB	⚠️ +5.12 kB
nextStartRea..uration (ms)	423ms	422ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
199-HASH.js gzip	30.7 kB	30.7 kB	N/A
3f784ff6-HASH.js gzip	53.3 kB	53.3 kB	✓
494.HASH.js gzip	180 B	181 B	N/A
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	241 B	239 B	N/A
main-HASH.js gzip	31.7 kB	31.7 kB	N/A
webpack-HASH.js gzip	1.7 kB	1.7 kB	✓
Overall change	100 kB	100 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
_app-HASH.js gzip	194 B	195 B	N/A
_error-HASH.js gzip	182 B	181 B	N/A
amp-HASH.js gzip	501 B	503 B	N/A
css-HASH.js gzip	322 B	323 B	N/A
dynamic-HASH.js gzip	2.5 kB	2.5 kB	✓
edge-ssr-HASH.js gzip	253 B	255 B	N/A
head-HASH.js gzip	348 B	347 B	N/A
hooks-HASH.js gzip	369 B	368 B	N/A
image-HASH.js gzip	4.27 kB	4.27 kB	N/A
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.61 kB	2.6 kB	N/A
routerDirect..HASH.js gzip	311 B	311 B	✓
script-HASH.js gzip	384 B	383 B	N/A
withRouter-HASH.js gzip	307 B	308 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.17 kB	3.17 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
_buildManifest.js gzip	484 B	483 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
index.html gzip	528 B	526 B	N/A
link.html gzip	538 B	541 B	N/A
withRouter.html gzip	524 B	523 B	N/A
Overall change	0 B	0 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
edge-ssr.js gzip	92.6 kB	92.6 kB	N/A
page.js gzip	146 kB	146 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
middleware-b..fest.js gzip	625 B	627 B	N/A
middleware-r..fest.js gzip	150 B	151 B	N/A
middleware.js gzip	35.7 kB	35.7 kB	N/A
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	1.92 kB	1.92 kB	✓

Next Runtimes

	vercel/next.js canary	vercel/next.js metadata/multi-others	Change
app-page-exp...dev.js gzip	168 kB	168 kB	✓
app-page-exp..prod.js gzip	93.7 kB	93.7 kB	N/A
app-page-tur..prod.js gzip	94.5 kB	94.5 kB	N/A
app-page-tur..prod.js gzip	89 kB	89 kB	N/A
app-page.run...dev.js gzip	138 kB	138 kB	✓
app-page.run..prod.js gzip	88.4 kB	88.4 kB	N/A
app-route-ex...dev.js gzip	24.2 kB	24.2 kB	✓
app-route-ex..prod.js gzip	16.8 kB	16.8 kB	✓
app-route-tu..prod.js gzip	16.9 kB	16.9 kB	✓
app-route-tu..prod.js gzip	16.4 kB	16.4 kB	✓
app-route.ru...dev.js gzip	23.6 kB	23.6 kB	✓
app-route.ru..prod.js gzip	16.4 kB	16.4 kB	✓
pages-api-tu..prod.js gzip	9.37 kB	9.37 kB	✓
pages-api.ru...dev.js gzip	9.64 kB	9.64 kB	✓
pages-api.ru..prod.js gzip	9.37 kB	9.37 kB	✓
pages-turbo...prod.js gzip	21.9 kB	21.9 kB	✓
pages.runtim...dev.js gzip	22.6 kB	22.6 kB	✓
pages.runtim..prod.js gzip	21.9 kB	21.9 kB	✓
server.runti..prod.js gzip	49.3 kB	49.3 kB	✓
Overall change	564 kB	564 kB	✓

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Commit: 0b7d7ef

[feedthejim]

should we edit the doc for that?

[huozhi]

@feedthejim Added the docs in 43a5240