fix: correctly check URL pathname with Cloudflare adapter

[teemingc]

fixes #8708
fixes #8736

I noticed a discrepancy where trailing slashes would be removed before checking if the file exists in manifest.prerendered.

This caused the pages with trailing slashes to never be found in the manifest.

Hopefully this fixes the issue for prerendered trailing slash pages that go through the Cloudflare worker.

Pages that manage to fit in the 100 rule limit for _routes.json do not go through the worker so they don't have this issue.

EDIT: expanded the scope of the PR to fix the URI encoding issue mismatch as well. It used to check the encoded pathname against the decoded paths in the manifest.

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@sveltejs/adapter-cloudflare	Patch

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[dummdidumm]

Could there theoretically be an asset named index.html? What was the reason for changing this?

[teemingc]

Could there theoretically be an asset named index.html?

If a dev decides to include one in /static I suppose. It helps if someone navigates to that route.
This check was already there previously, but I suppose it's good to have it since the worker has to handle all file routing.

What was the reason for changing this?

I thought it would be a small optimisation, although I'm unsure if it has an impact.

If the url is https://test.com/, then the resulting filename would be ''. This addition helps skip the manifest check for an empty string.