Alerting: Use Mimir image to run integration tests for the remote Alertmanager (#76608)

* Alerting: Use Mimir image to run integration tests for the remote Alertmanager

* skip integration test when running all tests

* skipping integration test when no Alertmanager URL is provided

* fix bad host for mimir_backend

* remove basic auth testing until we have an nginx image in our CI

scripts/drone/services/services.star

@@ -54,7 +54,7 @@ def integration_test_services():
             "commands": ["docker-entrypoint.sh mysqld --default-authentication-plugin=mysql_native_password"],
         },
         {
-            "name": "mimir",
+            "name": "mimir_backend",
             "image": images["mimir"],
             "environment": {},
             "commands": ["/bin/mimir -target=backend"],

scripts/drone/steps/lib.star

@@ -964,10 +964,16 @@ def redis_integration_tests_steps():
 def remote_alertmanager_integration_tests_steps():
     cmds = [
         "go clean -testcache",
-        "go test -run IntegrationRemoteAlertmanager -covermode=atomic -timeout=2m ./pkg/...",
+        "go test -run TestIntegrationRemoteAlertmanager -covermode=atomic -timeout=2m ./pkg/services/ngalert/notifier/...",
     ]
 
-    return integration_tests_steps("remote-alertmanager", cmds, "mimir", "8080", None)
+    environment = {
+        "AM_TENANT_ID": "test",
+        "AM_PASSWORD": "test",
+        "AM_URL": "http://mimir_backend:8080",
+    }
+
+    return integration_tests_steps("remote-alertmanager", cmds, "mimir_backend", "8080", environment = environment)
 
 def memcached_integration_tests_steps():
     cmds = [