[APM] switch get environment function to use terms_enum api

x-pack/plugins/apm/public/hooks/use_environments_fetcher.tsx

@@ -5,9 +5,9 @@
  * 2.0.
  */
 
+import { SERVICE_ENVIRONMENT } from '../../common/es_fields/apm';
 import { useFetcher } from './use_fetcher';
-
-const INITIAL_DATA = { environments: [] };
+import { Environment } from '../../common/environment_rt';
 
 export function useEnvironmentsFetcher({
   serviceName,
@@ -18,9 +18,13 @@ export function useEnvironmentsFetcher({
   start?: string;
   end?: string;
 }) {
-  const { data = INITIAL_DATA, status } = useFetcher(
+  const { data, status } = useFetcher(
     (callApmApi) => {
-      if (start && end) {
+      if (!start || !end) {
+        return;
+      }
+
+      if (serviceName) {
         return callApmApi('GET /internal/apm/environments', {
           params: {
             query: {
@@ -31,9 +35,24 @@ export function useEnvironmentsFetcher({
           },
         });
       }
+      return callApmApi('GET /internal/apm/suggestions', {
+        params: {
+          query: {
+            start,
+            end,
+            fieldName: SERVICE_ENVIRONMENT,
+            fieldValue: '',
+          },
+        },
+      });
     },
     [start, end, serviceName]
   );
 
-  return { environments: data.environments, status };
+  return {
+    environments: ((data as any)?.environments ||
+      (data as any)?.terms ||
+      []) as Environment[],
+    status,
+  };
 }

x-pack/plugins/apm/server/routes/environments/get_environments.ts

@@ -17,7 +17,7 @@ import { Environment } from '../../../common/environment_rt';
 import { APMEventClient } from '../../lib/helpers/create_es_client/create_apm_event_client';
 
 /**
- * This is used for getting the list of environments for the environments selector,
+ * This is used for getting the list of environments for the environment selector,
  * filtered by range.
  */
 export async function getEnvironments({