Add getCacheTTL() method to IReferenceProvider interface

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Is your feature request related to a problem? Please describe.

1. External API Integrations: Ticketing systems (Zammad, GitHub issues) with data that updates frequently
2. Configuration Management: Systems like iTop with dynamic configuration changes
3. Real-time Data: Any provider that needs sub-hourly cache invalidation

PR #56013 attempted to implement support for custom cache TTLs in the ReferenceManager, but discovered that the getCacheTTL() method referenced in issue #56012 does not actually exist in the IReferenceProvider interface.

Currently, ReferenceManager::resolveReference() always caches resolved references with a hardcoded 3600 second TTL, regardless of the provider's needs.

Current Behavior
Reference providers cannot specify custom cache durations. All cached references use the hardcoded CACHE_TTL = 3600 constant.

This is problematic for providers that manage frequently-changing data (e.g., external API integrations, ticketing systems, configuration management) that need shorter cache durations.

Describe the solution you'd like
Add a new optional method getCacheTTL() to the IReferenceProvider interface:

/**
 * Return the custom cache TTL for this provider's references in seconds
 * Return null to use the default CACHE_TTL (3600 seconds)
 *
 * @since 30.0.0
 * @return int|null The cache TTL in seconds, or null for default
 */
public function getCacheTTL(): ?int;

Describe alternatives you've considered
None

Additional context
Implementation Details

• The method should return an integer (seconds) or null (to use default 3600s)
• Makes it possible for ReferenceManager to respect provider-specific TTLs
• Maintains backward compatibility - providers that don't implement this method will default to 3600s
• Enables providers like external integrations to use shorter TTLs (e.g., 60-300 seconds) for real-time data

Start with the IReferenceProvider interface and ReferenceManager::resolveReference(), then review PR #56013 and issue #56012 for the surrounding cache-TTL context. The work is complete when providers can supply a TTL while references without one continue using the default 3600-second cache duration.