feat: add KVM performance timing metrics and monitoring

[nmgaston]

• Add Prometheus metrics for KVM API request tracking (amt_features, power_state, kvm_displays)
• Instrument WebSocket upgrade and connection setup timing
• Add device lookup, connection setup, and data transfer metrics
• Include baseline testing script for measuring API call patterns
• Add detailed KVM_TIMING debug logging throughout the connection flow

These metrics enable monitoring of KVM connection performance and identifying
redundant API calls for future optimization work.