Add db and vital metrics for clock and deployment_updater

[johha]

This change allows the export of database connection pool metrics and vital metrics for the cloud_controller_clock and cc_deployment_updater processes via prometheus.

This required some bigger changes:

Metrics Infrastructure

• Add ExecutionContext class to manage process type identification and rake context setup across all CAPI processes
• Add StandaloneMetricsWebserver for non-API processes (clock, deployment_updater, cc-worker) with automatic TLS configuration
• Refactor PrometheusUpdater to register metrics based on execution context, avoiding unnecessary metric registration
• Consolidate PrometheusUpdater instances (remove separate cc_worker_prometheus_updater)

Clock & Deployment Updater Configuration:

• Add publish_metrics config option to enable/disable metrics publishing
• Add prometheus_port config option (default: 9394 for clock, 9395 for deployment_updater)
• Initialize metrics webserver and periodic vital updates when metrics publishing is enabled

Metric Improvements:

• Add process_type and pid labels to vital metrics for process identification
• Add process_type label to DB connection pool metrics
• Refactor PeriodicUpdater to support configurable task lists (enables vitals-only updates for clock, deployment_updater, cc-worker)

Code Organization

• Rename MetricsWebserver to ApiMetricsWebserver for clarity
• Update all rake tasks to set execution context via ExecutionContext API
• Update DB connection metrics initialization to use ExecutionContext
• Update existing specs to work with new execution context

Links to any other associated PRs

• CAPI PR WIP

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• I have viewed, signed, and submitted the Contributor License Agreement

• I have made this pull request to the main branch

• I have run all the unit tests using bundle exec rake

• I have run CF Acceptance Tests