[APM][UI] Sort environment dropdown alphabetically (#217710)

Closes #217814

### Summary

Sort environment list alphabetically.

|Before|After|
|-|-|
|<img width="1724" alt="Screenshot 2025-04-10 at 12 01 15"
src="https://github.com/user-attachments/assets/53f0b66d-146a-45d9-b4e3-25bde350a263"
/>|<img width="1722" alt="Screenshot 2025-04-10 at 11 58 27"
src="https://github.com/user-attachments/assets/91315d23-801c-4a16-8688-c43d60c389c8"
/>|

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

@@ -54,6 +54,7 @@ export async function getEnvironments({
         terms: {
           field: SERVICE_ENVIRONMENT,
           missing: ENVIRONMENT_NOT_DEFINED.value,
+          order: { _key: 'asc' as const },
           size,
         },
       },

x-pack/solutions/observability/plugins/apm/server/routes/suggestions/get_suggestions_with_terms_aggregation.ts

@@ -51,7 +51,11 @@ export async function getSuggestionsWithTermsAggregation({
     },
     aggs: {
       items: {
-        terms: { field: fieldName, size },
+        terms: {
+          field: fieldName,
+          size,
+          order: { _key: 'asc' as const },
+        },
       },
     },
   });

x-pack/test/api_integration/deployment_agnostic/apis/observability/apm/environment/get_environment.spec.ts

@@ -104,10 +104,10 @@ export default function environmentsAPITests({ getService }: DeploymentAgnosticF
         expect(body.environments.length).to.be.equal(4);
         expectSnapshot(body.environments).toMatchInline(`
             Array [
+              "custom-go-environment",
               "development",
               "production",
               "staging",
-              "custom-go-environment",
             ]
           `);
       });