Fix metadata prop merging

[huozhi]

What

Fixes metadata merging issue on 14.2. There's a bug with React on 14.2 as it bit outdated: while generating rsc payload, if we use fragment to wrap the metadata and noindex component, it will miss all the data. It works well with separating them as an array.
It also requires #64058 to be applied as well so the output not-found page will having correct status 404, and then we can generate noindex metatag based on correct status

Fixes #69778

[ijjk]

Stats from current PR

Default Build

General

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
buildDuration	16.4s	14.8s	N/A
buildDurationCached	7.9s	7.1s	N/A
nodeModulesSize	200 MB	200 MB	N/A
nextStartRea..uration (ms)	401ms	408ms	N/A

Client Bundles (main, webpack)

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
1103-HASH.js gzip	31.6 kB	31.6 kB	N/A
1a9f679d-HASH.js gzip	53.7 kB	53.7 kB	N/A
335-HASH.js gzip	5.05 kB	5.05 kB	✓
7953.HASH.js gzip	181 B	181 B	✓
framework-HASH.js gzip	44.9 kB	44.9 kB	✓
main-app-HASH.js gzip	243 B	244 B	N/A
main-HASH.js gzip	32.2 kB	32.2 kB	N/A
webpack-HASH.js gzip	1.68 kB	1.68 kB	N/A
Overall change	50.1 kB	50.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
_app-HASH.js gzip	195 B	197 B	N/A
_error-HASH.js gzip	184 B	184 B	✓
amp-HASH.js gzip	501 B	506 B	N/A
css-HASH.js gzip	323 B	324 B	N/A
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edge-ssr-HASH.js gzip	259 B	258 B	N/A
head-HASH.js gzip	350 B	352 B	N/A
hooks-HASH.js gzip	372 B	371 B	N/A
image-HASH.js gzip	4.23 kB	4.23 kB	✓
index-HASH.js gzip	259 B	258 B	N/A
link-HASH.js gzip	2.68 kB	2.68 kB	N/A
routerDirect..HASH.js gzip	316 B	315 B	N/A
script-HASH.js gzip	387 B	387 B	✓
withRouter-HASH.js gzip	311 B	310 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	4.9 kB	4.9 kB	✓

Client Build Manifests

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
_buildManifest.js gzip	483 B	483 B	✓
Overall change	483 B	483 B	✓

Rendered Page Sizes

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
index.html gzip	529 B	528 B	N/A
link.html gzip	543 B	540 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 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
edge-ssr.js gzip	95.4 kB	95.4 kB	N/A
page.js gzip	3.06 kB	3.06 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
middleware-b..fest.js gzip	661 B	660 B	N/A
middleware-r..fest.js gzip	156 B	156 B	✓
middleware.js gzip	25.5 kB	25.5 kB	N/A
edge-runtime..pack.js gzip	839 B	839 B	✓
Overall change	995 B	995 B	✓

Next Runtimes

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
app-page-exp...dev.js gzip	171 kB	171 kB	N/A
app-page-exp..prod.js gzip	98 kB	98 kB	N/A
app-page-tur..prod.js gzip	99.8 kB	99.8 kB	N/A
app-page-tur..prod.js gzip	94 kB	94 kB	N/A
app-page.run...dev.js gzip	145 kB	145 kB	N/A
app-page.run..prod.js gzip	92.5 kB	92.5 kB	N/A
app-route-ex...dev.js gzip	22 kB	22 kB	✓
app-route-ex..prod.js gzip	15.4 kB	15.4 kB	✓
app-route-tu..prod.js gzip	15.4 kB	15.4 kB	✓
app-route-tu..prod.js gzip	15.2 kB	15.2 kB	✓
app-route.ru...dev.js gzip	21.7 kB	21.7 kB	✓
app-route.ru..prod.js gzip	15.2 kB	15.2 kB	✓
pages-api-tu..prod.js gzip	9.58 kB	9.58 kB	✓
pages-api.ru...dev.js gzip	9.85 kB	9.85 kB	✓
pages-api.ru..prod.js gzip	9.57 kB	9.57 kB	✓
pages-turbo...prod.js gzip	22.5 kB	22.5 kB	✓
pages.runtim...dev.js gzip	23.2 kB	23.2 kB	✓
pages.runtim..prod.js gzip	22.5 kB	22.5 kB	✓
server.runti..prod.js gzip	51.5 kB	51.5 kB	✓
Overall change	254 kB	254 kB	✓

build cache

	vercel/next.js 14-2-1	vercel/next.js fix/metadata-prop-merging	Change
0.pack gzip	1.61 MB	1.61 MB	N/A
index.pack gzip	113 kB	113 kB	N/A
Overall change	0 B	0 B	✓

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Commit: 236f04f

[ijjk]

Tests Passed