feat: add prometheus alerts in support bundle

[Yu-Jack]

Related Issue

https://github.com/harvester/harvester/issues/4993

Solution

For the first version of this feature, focus on fetching current alert.

I think If we fetch too many alerts here, it might be a problem for us debugging because it's too much and not easy to be queried. So, I just fetch current alert and format it.

Test Plan

Case 1. Generate support bundle without enabling rancher-monitoring, it should succeed as well, excluding prometheus-alerts.json. Case 2. Generate support bundle with enable rancher-monitoring, there should be a file called prometheus-alerts.json in first layer of directory.

Result

Sample, it only shows pending and firing state alert

[
	{
		"activeAt": "2024-01-23T06:59:00Z",
		"Annotations": {
			"description": "100% of the rancher/rancher targets in cattle-system namespace are down.",
			"runbook_url": "https://runbooks.prometheus-operator.dev/runbooks/general/targetdown",
			"summary": "One or more targets are unreachable."
		},
		"Labels": {
			"alertname": "TargetDown",
			"job": "rancher",
			"namespace": "cattle-system",
			"service": "rancher",
			"severity": "warning"
		},
		"State": "firing",
		"Value": "1e+02"
	},
	{
		"activeAt": "2024-01-24T07:37:00.510363907Z",
		"Annotations": {
			"description": "This is an alert meant to ensure that the entire alerting pipeline is functional.\nThis alert is always firing, therefore it should always be firing in Alertmanager\nand always fire against a receiver. There are integrations with various notification\nmechanisms that send a notification when this alert is not firing. For example the\n\"DeadMansSnitch\" integration in PagerDuty.\n",
			"runbook_url": "https://runbooks.prometheus-operator.dev/runbooks/general/watchdog",
			"summary": "An alert that should always be firing to certify that Alertmanager is working properly."
		},
		"Labels": {
			"alertname": "Watchdog",
			"severity": "none"
		},
		"State": "firing",
		"Value": "1e+00"
	},
        // ignore others for reading...
]