fix(core) : Resolve relative URLs when enhancing fetch error messages

[kunal649]

enhanceFetchErrorMessages already adds the host to generic fetch errors, so Failed to fetch becomes Failed to fetch (example.com). The catch is that it ran new URL(url) with no base, and that throws for relative URLs like /api/foo or the fetch("") from the issue. The try/catch swallowed the error, so those requests never got the host.

Now relative URLs are resolved against location.origin if there is one (the browser tracing code already passes the same thing as urlBase). Absolute URLs ignore the base, and where there's no location (Node, workers) nothing changes. I also skip the enhancement when the resolved host is empty, like on file:// pages, otherwise you'd get Failed to fetch (). location is added to InternalGlobal for the typing.

I added six unit tests (relative URL, empty URL, no location, file:// origin, opaque null origin, absolute URL on another origin).

This only touches the error message. The empty URL in the fetch breadcrumbs is a separate spot, so I left it out to discuss on the issue thread.

Fixes #13168

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[s1gr1d]

Thank you so much for picking this up!

a small nit regarding the tests: they are all quite similar so you could use an it.each there, like this:

    it.each([
      ['a relative path', 'https://app.example.com/dashboard?tab=billing', '/api/users/42', 'Failed to fetch (app.example.com)'],
    ])('resolves %s against location.href', async (_name, href, target, expected) => {}

[s1gr1d]

following the other comment

Suggested change

	location?: { origin?: string };
	location?: { href?: string };