fix: prevent URL mutation in router rewrites (#83963)
### What?
This PR fixes critical URL mutation issues in Next.js routing that were
causing state pollution between requests and breaking compatibility
between App Router and Pages Router during rewrite handling.
### Why?
Several interconnected problems were discovered in the routing system:
1. **URL Object Mutation**: The original `parsedUrl` objects were being
mutated during rewrite processing, causing state to leak between
requests and potentially affecting subsequent routing decisions.
2. **Router Type Confusion**: The routing system lacked explicit
tracking of whether a route belonged to the App Router or Pages Router,
leading to incorrect query parameter handling and normalization logic
being applied inconsistently.
3. **Query Parameter Pollution**: App Router RSC payloads were being
polluted with rewrite query parameters that should only be applied to
Pages Router routes, breaking the separation of concerns between the two
routing systems.
4. **Catch-all Route Normalization**: Pages Router catch-all routes
require specific array normalization (e.g., `["hello", "world"]`) but
this was being applied inconsistently or to the wrong router type.
5. **Middleware Filtering Bypass**: The x-matched-path header handling
was bypassing proper middleware query filtering in deployment scenarios.
These issues manifested as test failures where Pages Router catch-all
routes weren't receiving proper array values, App Router routes were
getting contaminated with rewrite parameters, and the routing behavior
was inconsistent between development and deployment environments.
### Dependant PR's
https://github.com/vercel/vercel/pull/13927
[NAR-398](https://linear.app/vercel/issue/NAR-398)
