fix: normalize html path in transformIndexHtml()

[vanaigr]

Problem

Currently, the url accepted by transformIndexHtml() is passed unaltered to applyHtmlTransforms().This causes issues if the url

1. doesn't refer to a file (see SSR dev server "Pre-transform error: Failed to load url" for relative path #18964), or
2. contains search parameters or hash (/index.html?a=b or index.html#id).

This is different from how default vite server and build behave; they use urls that refer to a file. (The server modifies urls in htmlFallbackMiddleware()).

Solution

I extracted html path normalization from htmlFallbackMiddleware() and used it in createDevHtmlTransformFn().

Fixes #18964

[vanaigr]

Also noticed that SSR guide uses req.originalUrl as the html url.

Not sure if this is known, but it doesn't work with base config option since the base removing middleware doesn't affect originalUrl.