Fix regression on dynamic sibling trees and index inside rest parameter folders

[Fryuni]

Changes

• Fixes Dynamic folder routes ([...rest]/index.astro) take precedence over index.astro in 4.2.1 #9770
• Fixes Routing priority incorrect for deeply-matched dynamic routes #9779

Testing

The new test includes a nested structure of dynamic parameters as folders with indexes, including rest parameters in the middle of the route.

Docs

The rules remain the same but now apply per-segment instead of the whole route at once.
Unclear to me whether this needs to be made more clear on the docs.

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[ematipico]

Unclear to me whether this needs to be made more clear on the docs.

Since this is a soft subject, I believe we should be clear as much as we can. I think it's valuable to add more clarification in our docs

[ematipico]

I think the change is good! Just added feedback around adding more cases. After that, we can merge it and ship it

[natemoo-re]

Looks good to me!