feat(symfony): add routePriority to control route matching order

[soyuka]

Summary

Adds a new nullable ?int $routePriority operation attribute that maps to the third argument of Symfony's RouteCollection::add(string $name, Route $route, int $priority = 0), controlling the URL-matching precedence of the route generated for an operation.

This is distinct from the existing priority attribute, which sorts operations within a resource via Operations::sort(). routePriority instead controls cross-route matching order in the Symfony router, which the per-resource sort does not cover.

Wired through all HTTP operation subclasses (Get, GetCollection, Post, Put, Patch, Delete, NotExposed, McpResource, McpTool) plus the YAML/XML extractors and XSD schema, so it is configurable from every metadata format.

Test plan

• ApiLoaderTest asserts an operation with routePriority: N registers the route at priority N, and that an operation without it stores no priority.
• tests/Symfony/Routing green (5/5).
• PHPStan + php-cs-fixer clean on changed files.

Closes #8135