Add check to ensure PHP Runtime (OPcache) is enabled.

Problem/Motivation

The PHP runtime may not have OPcache enabled or optimally configured, which can lead to unnecessary PHP re-compilation on every request, reduced performance, and inefficient use of server resources.

Steps to reproduce

Proposed resolution

Add a new Performace FitCheck plugin PhpOpcacheConfigurationCheck that:

• Detects whether PHP OPcache is enabled in the current runtime used by the Drupal site.
• Checks key OPcache settings (for example, opcache.enable, opcache.memory_consumption, opcache.max_accelerated_files, and opcache.validate_timestamps) against recommended baseline values for production.
• Fails with FitWeight::Medium when OPcache is disabled or clearly misconfigured, and provides a brief help message pointing to recommended production settings.

Remaining tasks

User interface changes

API changes

Data model changes