Fix trailing slash for canonical url

[huozhi]

What

We should respect the trailingSlash config for metadata canonical url, this PR is adding the handling for strip or keep the trailing slash for canonical url. Passing down trailingSlash config to metadata resolving to decide how we handle it.

Why

The tricky one was / pathname, when visiting the origin directly, that it will always have at least / in the URL instance. But for the default origin, it shouldn't show the / if the trailingSlash config is false. Also it should show trailing slash for all pathnames if that config is enabled.

BTW there's a __NEXT_TRAILING_SLASH env but since we're using the fixed nextjs runtime module, so this can't be dynamically replaced in the metadata resolving modules. So we didn't use it

Fixes #54070
Closes NEXT-2424

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
buildDuration	21.9s	22s	⚠️ +138ms
buildDurationCached	9.4s	7.9s	N/A
nodeModulesSize	196 MB	196 MB	⚠️ +20.3 kB
nextStartRea..uration (ms)	438ms	442ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
1068-HASH.js gzip	30.2 kB	30.2 kB	N/A
3f784ff6-HASH.js gzip	53.5 kB	53.5 kB	N/A
4944-HASH.js gzip	5.04 kB	5.03 kB	N/A
8423.HASH.js gzip	181 B	181 B	✓
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	241 B	242 B	N/A
main-HASH.js gzip	32.1 kB	32.1 kB	N/A
webpack-HASH.js gzip	1.7 kB	1.7 kB	✓
Overall change	47.1 kB	47.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
_app-HASH.js gzip	196 B	196 B	✓
_error-HASH.js gzip	184 B	183 B	N/A
amp-HASH.js gzip	503 B	504 B	N/A
css-HASH.js gzip	323 B	324 B	N/A
dynamic-HASH.js gzip	2.5 kB	2.51 kB	N/A
edge-ssr-HASH.js gzip	258 B	259 B	N/A
head-HASH.js gzip	353 B	351 B	N/A
hooks-HASH.js gzip	370 B	370 B	✓
image-HASH.js gzip	4.21 kB	4.2 kB	N/A
index-HASH.js gzip	259 B	259 B	✓
link-HASH.js gzip	2.68 kB	2.67 kB	N/A
routerDirect..HASH.js gzip	313 B	314 B	N/A
script-HASH.js gzip	386 B	385 B	N/A
withRouter-HASH.js gzip	309 B	311 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	931 B	931 B	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
_buildManifest.js gzip	485 B	484 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
index.html gzip	529 B	529 B	✓
link.html gzip	541 B	541 B	✓
withRouter.html gzip	525 B	524 B	N/A
Overall change	1.07 kB	1.07 kB	✓

Edge SSR bundle Size Overall increase ⚠️

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
edge-ssr.js gzip	94.4 kB	94.5 kB	N/A
page.js gzip	151 kB	151 kB	⚠️ +105 B
Overall change	151 kB	151 kB	⚠️ +105 B

Middleware size

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
middleware-b..fest.js gzip	625 B	624 B	N/A
middleware-r..fest.js gzip	151 B	151 B	✓
middleware.js gzip	44.4 kB	44.4 kB	N/A
edge-runtime..pack.js gzip	1.94 kB	1.94 kB	✓
Overall change	2.1 kB	2.1 kB	✓

Next Runtimes

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
app-page-exp...dev.js gzip	166 kB	166 kB	N/A
app-page-exp..prod.js gzip	95.5 kB	95.6 kB	N/A
app-page-tur..prod.js gzip	97.3 kB	97.3 kB	N/A
app-page-tur..prod.js gzip	91.7 kB	91.8 kB	N/A
app-page.run...dev.js gzip	136 kB	136 kB	N/A
app-page.run..prod.js gzip	90.3 kB	90.3 kB	N/A
app-route-ex...dev.js gzip	22 kB	22 kB	✓
app-route-ex..prod.js gzip	14.9 kB	14.9 kB	✓
app-route-tu..prod.js gzip	14.9 kB	14.9 kB	✓
app-route-tu..prod.js gzip	14.6 kB	14.6 kB	✓
app-route.ru...dev.js gzip	21.7 kB	21.7 kB	✓
app-route.ru..prod.js gzip	14.6 kB	14.6 kB	✓
pages-api-tu..prod.js gzip	9.43 kB	9.43 kB	✓
pages-api.ru...dev.js gzip	9.7 kB	9.7 kB	✓
pages-api.ru..prod.js gzip	9.43 kB	9.43 kB	✓
pages-turbo...prod.js gzip	22 kB	22 kB	✓
pages.runtim...dev.js gzip	22.7 kB	22.7 kB	✓
pages.runtim..prod.js gzip	22 kB	22 kB	✓
server.runti..prod.js gzip	50 kB	50 kB	N/A
Overall change	198 kB	198 kB	✓

build cache Overall increase ⚠️

	vercel/next.js canary	vercel/next.js fix/index-canonical-url	Change
0.pack gzip	1.55 MB	1.55 MB	N/A
index.pack gzip	103 kB	104 kB	⚠️ +398 B
Overall change	103 kB	104 kB	⚠️ +398 B

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Commit: 5345053