Implemented countries host check (#5713)

* Added check and alert implementation

* Fixed size of estimation and some typo

* Added HLL counters and DES structure
Co-authored-by: Paolo Junior Mollica <p.mollica@studenti.unipi.it>

* fixes according comments of PR

* decreased memory footprint

* resolved conflicts

* fixed HostCheckID

* Removed wrongly committed file

Co-authored-by: paolo-junior-mollica <paolo.junior.mollica@gmail.com>
Co-authored-by: Matteo Biscosi <49585191+MatteoBiscosi@users.noreply.github.com>

scripts/lua/modules/check_definitions/host/countries_contacts.lua

@@ -0,0 +1,35 @@
+--
+-- (C) 2019-21 - ntop.org
+--
+
+local checks = require("checks")
+local host_alert_keys = require "host_alert_keys"
+
+-- #################################################################
+
+local countries_contacts = {
+   -- Script category
+   category = checks.check_categories.security,
+
+   default_enabled = false,
+   alert_id = host_alert_keys.host_alert_countries_contacts,
+
+   default_value = {
+      operator = "gt",
+      threshold = 100,
+   },
+
+   gui = {
+      i18n_title = "alerts_thresholds_config.countries_contacts_title",
+      i18n_description = "alerts_thresholds_config.countries_contacts_description",
+      i18n_field_unit = checks.field_units.contacts,
+      input_builder = "threshold_cross",
+      field_max = 255,
+      field_min = 1,
+      field_operator = "gt";
+   }
+}
+
+-- #################################################################
+
+return countries_contacts