feat(openapi): implement ResetInterface in OpenApiFactory

[KevinMartinsDev]

Description

This PR is the fourth part of the worker mode compatibility audit (see #7918). It implements ResetInterface in OpenApiFactory to handle internal state persistence.

The Issue

OpenApiFactory is a singleton service that maintains two types of internal state:

1. Route Collection Cache: Once the router is accessed, the RouteCollection is stored in a private property.
2. Local Error Resource Cache: A private array ($localErrorResourceCache) that stores resolved error resources to avoid redundant processing.

In persistent memory environments like FrankenPHP:

• Stale Data: If routes are modified or dynamically updated, the factory might keep using the old cached RouteCollection until the worker restarts.
• Memory Growth: The error resource cache grows with every unique error encountered, leading to an unbounded increase in RAM usage over time.

The Solution

By implementing Symfony\Contracts\Service\ResetInterface, we ensure that:

• $routeCollection is reset to null.
• $localErrorResourceCache is cleared (reset to []).

This happens automatically after each request in worker mode, ensuring that the next request starts with fresh metadata and a clean memory footprint.