Alerting: Add MissingSeriesEvalsToResolve to the APIs (#102150)

What is this feature?

A follow-up for #101184, adds AlertRule.MissingSeriesEvalsToResolve to the APIs.

missing_series_evals_to_resolve must be specified too and it must be > 0.

POST /api/ruler/grafana/api/v1/rules/{folderUID} works in the following way:

    If missing_series_evals_to_resolve is not sent or null, the rule keeps its existing value
    If missing_series_evals_to_resolve > 0: updates to that value
    If missing_series_evals_to_resolve = 0: resets to default (nil).
    AlertRule.MissingSeriesEvalsToResolve can't be 0, so I used it to reset

In the Provisioning API, the value is just set if present and > 0. Otherwise it's reset:

PUT to /api/v1/provisioning/alert-rules/{UID}:

    If missing_series_evals_to_resolve is nil, it's reset to the default value
    If missing_series_evals_to_resolve > 0, it's updated

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

@@ -4442,6 +4442,10 @@
             "type": "string"
           }
         },
+        "missing_series_evals_to_resolve": {
+          "type": "integer",
+          "format": "int64"
+        },
         "noDataState": {
           "type": "string",
           "enum": [
@@ -5855,6 +5859,10 @@
         "metadata": {
           "$ref": "#/definitions/AlertRuleMetadata"
         },
+        "missing_series_evals_to_resolve": {
+          "type": "integer",
+          "format": "int64"
+        },
         "namespace_uid": {
           "type": "string"
         },
@@ -7090,6 +7098,12 @@
         "metadata": {
           "$ref": "#/definitions/AlertRuleMetadata"
         },
+        "missing_series_evals_to_resolve": {
+          "description": "Number of consecutive evaluation intervals with no data for a dimension must pass\nbefore the alert state is considered stale and automatically resolved.\nIf set to 0, the value is reset to the default.",
+          "type": "integer",
+          "format": "int64",
+          "example": 3
+        },
         "no_data_state": {
           "type": "string",
           "enum": [
@@ -7387,6 +7401,11 @@
             "team": "sre-team-1"
           }
         },
+        "missingSeriesEvalsToResolve": {
+          "type": "integer",
+          "format": "int64",
+          "example": 2
+        },
         "noDataState": {
           "type": "string",
           "enum": [
@@ -9039,7 +9058,6 @@
       }
     },
     "alertGroups": {
-      "description": "AlertGroups alert groups",
       "type": "array",
       "items": {
         "type": "object",
@@ -9201,7 +9219,6 @@
       }
     },
     "gettableAlerts": {
-      "description": "GettableAlerts gettable alerts",
       "type": "array",
       "items": {
         "type": "object",