Alerting: Support query_offset in the Prometheus conversion (#102499)

Adds support for rule group-level query_offset in Prometheus to Grafana rule conversion. It allows specifying a time offset for rule evaluation, which gets applied and saved during the conversion.

pkg/services/ngalert/api/tooling/api.json

@@ -208,6 +208,9 @@
     "isPaused": {
      "type": "boolean"
     },
+    "keepFiringFor": {
+     "$ref": "#/definitions/Duration"
+    },
     "labels": {
      "additionalProperties": {
       "type": "string"
@@ -468,6 +471,10 @@
     "health": {
      "type": "string"
     },
+    "keepFiringFor": {
+     "format": "double",
+     "type": "number"
+    },
     "labels": {
      "$ref": "#/definitions/Labels"
     },
@@ -3012,9 +3019,22 @@
     "Interval": {
      "$ref": "#/definitions/Duration"
     },
+    "Labels": {
+     "additionalProperties": {
+      "type": "string"
+     },
+     "type": "object"
+    },
+    "Limit": {
+     "format": "int64",
+     "type": "integer"
+    },
     "Name": {
      "type": "string"
     },
+    "QueryOffset": {
+     "type": "string"
+    },
     "Rules": {
      "items": {
       "$ref": "#/definitions/PrometheusRule"
@@ -3117,6 +3137,10 @@
      "example": false,
      "type": "boolean"
     },
+    "keep_firing_for": {
+     "format": "duration",
+     "type": "string"
+    },
     "labels": {
      "additionalProperties": {
       "type": "string"
@@ -4952,7 +4976,6 @@
    "type": "object"
   },
   "gettableAlerts": {
-   "description": "GettableAlerts gettable alerts",
    "items": {
     "$ref": "#/definitions/gettableAlert",
     "type": "object"