[8.x] [APM][UI] Sort environment dropdown alphabetically (elastic#217710) (elastic#217878)

# Backport

This will backport the following commits from `main` to `8.x`:
- [[APM][UI] Sort environment dropdown alphabetically
(elastic#217710)](elastic#217710)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

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Sort environment dropdown alphabetically (elastic#217710)\n\nCloses
elastic#217814\n\n### Summary\n\nSort environment list
alphabetically.\n\n|Before|After|\n|-|-|\n|<img width=\"1724\"
alt=\"Screenshot 2025-04-10 at 12 01
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Sort environment dropdown
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Sort environment dropdown alphabetically (elastic#217710)\n\nCloses
elastic#217814\n\n### Summary\n\nSort environment list
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alt=\"Screenshot 2025-04-10 at 12 01
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BACKPORT-->

---------

Co-authored-by: kibanamachine <[email protected]>

Author: miloszmarcinkowski

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

@@ -55,6 +55,7 @@ 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

@@ -52,7 +52,11 @@ 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",
             ]
           `);
       });