Update alerts list to fail gracefully on GraphQL failure

...ripts/threat_monitoring/components/alerts/alerts_list.vue

ee/changelogs/unreleased/294185-update-alert-list-tests.yml

.../threat_monitoring/components/alerts/alert_status_spec.js

...d/threat_monitoring/components/alerts/alerts_list_spec.js

...d/threat_monitoring/components/environment_picker_spec.js

.../threat_monitoring/components/network_policy_list_spec.js

...d/threat_monitoring/components/statistics_history_spec.js

...t_monitoring/components/threat_monitoring_filters_spec.js

...t_monitoring/components/threat_monitoring_section_spec.js

ee/spec/frontend/threat_monitoring/mocks/mock_apollo.js

ee/spec/frontend/threat_monitoring/mocks/mock_data.js

...monitoring/store/modules/network_policies/actions_spec.js

...onitoring/store/modules/threat_monitoring/actions_spec.js

...tore/modules/threat_monitoring_statistics/actions_spec.js

...re/modules/threat_monitoring_statistics/mutations_spec.js