fix: inline server stylesheets instead of client stylesheets

[eltigerchino]

fixes #6720

This PR changes the inlined stylesheet from client to server so that the paths for imported assets in the CSS such as fonts are correct when the document first loads. In comparison, the client stylesheet links are relative by default, so they always link to the wrong place

e.g., URL("./font.woff") links to example.com/font.woff when loaded from the document instead of example.com/_app/immutable/.... However, when loaded from an external stylesheet, the link is correct because the stylesheet is already loaded from /_app/immutable/....

TODO:

• find a more reliable way of mapping client stylesheets to server stylesheets

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[dummdidumm]

Just for understanding: asset.fileName is always different between client and server, i.e. there's no chance of this accidentally filtering out a server stylesheet?

[eltigerchino]

Yeah, they're always different. The client stylesheets correspond to the node index number while server stylesheets are always "_page" or "_layout".

[Rich-Harris]

preview: https://svelte-dev-git-preview-kit-13068-svelte.vercel.app/

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