fix(react-router): route-context being available and loaders being called after a redirection

[SeanCassiere]

This PR initially was just to add tests for the route-context checks after navigation, but it became a bit more.

• It checks route context being available after a navigation.
• It checks route context being available after a redirection.
• It checks that the destination route loaders are being fired when redirected to.
• The tests introduced in test(react-router): check the availability of the route context after a redirect on the first load #1710 are also being amended to better simulate a "real-world experience". No more relying on calls to router.navigate(), instead a button is clicked which calls navigate from useNavigate().
• The tests in packages/react-router/tests/redirects.test.tsx related to route-context have been REMOVED in favor of the ones in packages/react-router/tests/routeContext.test.tsx as they simulate real-world usage.

I've manually tested these changes against the reproductions in the following issues and can confirm that this PR fixes the following.

• Undefined context in loader after redirect #1730
• Undefined context after redirect #1670
• Undefined context after redirect with wrapInSuspense at root route (introduced in 1.33.6) #1650
• This comment in Context is undefined when search validation fails #1656

Context-related issues still remain broken in this though.

• The original reproduction in Context is undefined when search validation fails #1656

Thanks to @freshgiammi pointing out the unnecessary this.load().

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[SeanCassiere]

The fix pointed out by @freshgiammi.

[SeanCassiere]

Removed since this is no longer representative of what's actually happening in the browser.
Plus these test-cases are already covered in tests/routeContext.test.tsx.

[krambono]

Hello,

It seems that this version introduced a bug.

I have a simple router with an index.tsx that redirects to a login page with beforeLoad:

export const Route = createFileRoute('/')({
  beforeLoad: () => {
    throw redirect({ to: '/login' });
  },
});

export const Route = createFileRoute('/login')({
  component: Login,
});

When I refresh my browser on "/", I get a blank page.

It was working in previous versions.

I can provide the entire code later.

[TkDodo]

I noticed that writing to the context of one route will now overwrite the context of all routes, so the router context is no longer isolated per route.

this is confirmed working in v1.36.2 but no longer in v1.36.3, and this release just has this fix, so I think we can trace it back here

compare this breadcrumbs example on:

• v1.36.2
  

• v1.36.3