refactor(router): add support for non-blocking router resources - #70211

… feature

Activated Route Injector feature was developed for resources. This moves the internal
naming (files and vars) to reflect this now that we have landed the core bits of plumbing
and are ready to implement router resources.

Introduces support for route-level resources via the `resources` property on route definitions, enabled with `withRouterResources()`.

Router resources provide a reactive, signal-based alternative to resolvers, allowing routes to declare resources tied to route parameters and route lifecycle:
- The `resources` function executes during navigation transitions within an injection context scoped to the route (`_localInjector`).
- It receives a `ResourceContext` containing signals for `params`, `queryParams`, `fragment`, and `data`, alongside the static `snapshot`.
- For newly created routes, `resources` runs once and attaches to `ActivatedRoute.resources`. For reused routes, parameter signals update reactively to trigger new data fetches while keeping resource references stable.
- Wrapped resources (`routerResource`) provide transactional stability: snapshots are frozen during active navigations to prevent UI jitter, unfreezing on `NavigationEnd`.
- On cancelled navigations or errors, rollback recovery retains the frozen snapshot until reverted signals settle, avoiding flashes of loading state. Manual reloads are rejected while frozen.
- Local injectors are automatically cleaned up if navigations are cancelled or rolled back.

Note that this commit only implements non-blocking resources (marked with `nonBlocking()`), deferring blocking resource resolution to future work to keep the initial changeset smaller and less complex.