Add support for multiple targets

[prologic]

Example prometheus job config:

  - job_name: 'pve'
    static_configs:
      - targets:
        - 10.0.0.1  # Proxmox Server #1
        - 10.0.0.2  # Proxmox Server #2
    metrics_path: /metrics
    relabel_configs:
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [__param_target]
        target_label: instance
      - target_label: __address__
        replacement: pve_exporter:9090  # pve_exporter