[fix] handle redirects in handle hook while processing data request

[dummdidumm]

Fixes #7787

During fixing this, I wondered why the tests also pass without the fix, and discovered that this specific behavior will only occur if there's no root +layout.server.js (because then it wouldn't try to rerequest the data, failing again, resulting in a fallback to the server where the redirect would be handled correctly), which we have in the tests. I'm not sure if it's worth creating another test suite for this, so I left it like this.

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[styxpilled]

Reading this surprised me, because I found this issue in a project that had +layout.server.js. After some tests I here's what I found:

• if you redirect in hooks.server.js and you don't have +layout.server.js, kit will load that route. If you have +page.server.js in that route, it will fail with a 500 error.
• if you have +layout.server.js, the redirect will work.
• but then if you don't have +page.server.js, the redirect won't work.
  • if you have a +page.js that fetches some stuff from an endpoint (which you may also be blocking with hooks) that fails, the page will fail with a 500 error.
  • if you don't have that, the page will display as normal, even though it shouldn't.