Remove assumptions around having an index.html that are incompatible with SSR

[benmccann]

Clear and concise description of the problem

When rendering a page via SSR we cannot assume that Vite will be serving an index.html page. Rather, in SSR the page contents are dynamically generated at runtime. E.g. in SvelteKit we want requests to be served with our middleware and so we have to remove these middlewares that are incompatible.

Suggested solution

Need a cleaner way to disable viteIndexHtmlMiddleware, vite404Middleware, and viteSpaFallbackMiddleware

Might also want to think about whether transformIndexHtml makes sense

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[bluwy]

Related: #5720

Maybe having a server.middlewares.<middlewareName>: Config | false option would help solve these issues collectively, but now it exposes more options.

[brillout]

There is work about this over there #8061.

[benmccann]

This is mostly done now. See #7665