Proxmox quorum status

### Use Case

Actually, the proxmox input plugin is only to gather VMs info, but do not give any informations about the cluster state.

Reporting the quorum state and stats about votes, etc... would help to create alerts.

### Expected behavior

Reporting VMs stats + quorum state (and probably some other stats)

### Actual behavior

Reporting VMs stats

### Additional info

_No response_

Start by locating the Proxmox input plugin and reading how it currently gathers VM statistics. Determine how quorum state, vote counts, and related cluster metrics should be represented, then verify that the plugin reports them alongside VM stats and that the expected alerts can use those metrics.

Written by the indexing model from the issue text.