Alerts changes

NOTE: database schema changed. Existing alerts will be lost.

- Unified engaged and closed tables
- Simplified hosts engaged alert counters handling: periodically set by lua
- Removed alert engine and replaced with alert periodicity
- Now engage is implicitly derived from the alert end timestamp and periodicity
- New alerts_api.lua to easily emit alerts
- Removed past alerts counter aggregation by hash
- Alert notifications for non-flow alerts are now removed from C and triggered by lua

scripts/lua/modules/test/test_utils.lua

@@ -4,9 +4,15 @@
 
 local test_utils = {}
 
+local alerts = require("alerts_api")
+local test_failed_alert = alerts:newAlert({
+  type = "test_failed",
+  entity = "test"
+  severity = "error",
+})
+
 local function test_error(msg)
-   interface.storeAlert(alertEntity("test"), "test",
-    			alertType("test_failed"), alertSeverity("error"), msg)
+  test_failed_alert:emit("test", msg)
 end
 
 local function test_assert(cond, error_msg)