Skip scheduling actions for the alerts without scheduledActions (elas…

…tic#195948)

Resolves: elastic#190258

As a result of elastic#190258, we have found out that the odd behaviour happens
when an existing alert is pushed above the max alerts limit by a new
alert.

Scenario:

1. The rule type detects 4 alerts (`alert-1`, `alert-2`, `alert-3`,
`alert-4`),
But reports only the first 3 as the max alerts limit is 3.

2. `alert-2` becomes recovered, therefore the rule type reports 3 active
(`alert-1`, `alert-3`, `alert-4`), 1 recovered (`alert-2`) alert.

3. Alerts `alert-1`,  `alert-3`, `alert-4` are saved in the task state.

4. `alert-2` becomes active again (the others are still active)

5. Rule type reports 3 active alerts (`alert-1`,  `alert-2`, `alert-3`)

6. As a result, the action scheduler tries to schedule actions for
`alert-1`, `alert-3`, `alert-4` as they are the existing alerts.
But, since the rule type didn't report the `alert-4` it has no scheduled
actions, therefore the action scheduler assumes it is recovered and
tries to schedule a recovery action.

This PR changes the actionScheduler to handle active and recovered
alerts separately.
With this change, no action would be scheduled for an alert from
previous run (exists in the task state) and isn't reported by the
ruleTypeExecutor due to max-alerts-limit but it would be kept in the
task state.

x-pack/plugins/alerting/server/alerts_client/types.ts

@@ -77,8 +77,11 @@ export interface IAlertsClient<
   processAlerts(opts: ProcessAlertsOpts): void;
   logAlerts(opts: LogAlertsOpts): void;
   getProcessedAlerts(
-    type: 'new' | 'active' | 'activeCurrent' | 'recovered' | 'recoveredCurrent'
-  ): Record<string, LegacyAlert<State, Context, ActionGroupIds | RecoveryActionGroupId>>;
+    type: 'new' | 'active' | 'activeCurrent'
+  ): Record<string, LegacyAlert<State, Context, ActionGroupIds>> | {};
+  getProcessedAlerts(
+    type: 'recovered' | 'recoveredCurrent'
+  ): Record<string, LegacyAlert<State, Context, RecoveryActionGroupId>> | {};
   persistAlerts(): Promise<{ alertIds: string[]; maintenanceWindowIds: string[] } | null>;
   isTrackedAlert(id: string): boolean;
   getSummarizedAlerts?(params: GetSummarizedAlertsParams): Promise<SummarizedAlerts>;