Add PHP runtime PHM meter analyzer, e2e, and documentation

[songzhendong]

Add PHP runtime PHM meter analyzer, e2e, and documentation

This PR adds OAP support for PHP Health Metrics (PHM) reported by the SkyWalking PHP agent.

• Introduce php-runtime.yaml MAL analyzer registering six instance-level meters on the General Service layer:
  • meter_instance_php_process_cpu_utilization
  • meter_instance_php_memory_used_mb
  • meter_instance_php_memory_peak_mb
  • meter_instance_php_virtual_memory_mb
  • meter_instance_php_thread_count
  • meter_instance_php_open_fd_count
• Add php-runtime to default meterAnalyzerActiveFiles.
• Pin SW_AGENT_PHP_COMMIT to merged PHM agent release de311c9.
• Set metrics_report_period=31 in e2e php.ini so meter gRPC streams idle-close and OAP persists PHM samples reliably.

PHM process meters are Linux-only (agent samples /proc via getppid() for the parent PHP process).

• If this is non-trivial feature, paste the links/URLs to the design doc.

  • Agent-side PHM merged in Add PHP Health Metrics (PHM) with /proc-based worker collection skywalking-php#145; no separate SWIP.

• Update the documentation to include this new feature.

  • docs/en/setup/backend/dashboards-php-runtime.md; update backend-meter.md, menu.yml, and CHANGES.

• Tests(including UT, IT, E2E) are added to verify the new feature.

  • MAL data tests: php-runtime.data.yaml
  • PHP e2e: six meter_instance_php_* assertions in test/e2e-v2/cases/php/e2e.yaml
  • Fork Agent PHP e2e passed before opening (fork run; overall workflow may show red when unrelated e2e matrix jobs fail)

• If it's UI related, attach the screenshots below.

  • Horizon UI widgets ship separately in apache/skywalking-horizon-ui.

• If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes #.

• Update the CHANGES log.