Split up and clarify Enterprise Search codeowners (#76580)

@elastic/enterprise-search-frontend is a shared team of both app-search-frontend and workplace-search-frontend, but combining it into one group means only 1 reviewer is required (as opposed to 1 per team).

.github/CODEOWNERS

@@ -209,8 +209,19 @@ x-pack/plugins/telemetry_collection_xpack/schema/xpack_plugins.json @elastic/kib
 /x-pack/test/functional_with_es_ssl/fixtures/plugins/alerts/ @elastic/kibana-alerting-services
 
 # Enterprise Search
-/x-pack/plugins/enterprise_search/ @elastic/app-search-frontend @elastic/workplace-search-frontend
-/x-pack/test/functional_enterprise_search/ @elastic/app-search-frontend @elastic/workplace-search-frontend
+# Shared
+/x-pack/plugins/enterprise_search/ @elastic/enterprise-search-frontend
+/x-pack/test/functional_enterprise_search/ @elastic/enterprise-search-frontend
+# App Search
+/x-pack/plugins/enterprise_search/public/applications/app_search @elastic/app-search-frontend
+/x-pack/plugins/enterprise_search/server/routes/app_search @elastic/app-search-frontend
+/x-pack/plugins/enterprise_search/server/collectors/app_search @elastic/app-search-frontend
+/x-pack/plugins/enterprise_search/server/saved_objects/app_search @elastic/app-search-frontend
+# Workplace Search
+/x-pack/plugins/enterprise_search/public/applications/workplace_search @elastic/workplace-search-frontend
+/x-pack/plugins/enterprise_search/server/routes/workplace_search @elastic/workplace-search-frontend
+/x-pack/plugins/enterprise_search/server/collectors/workplace_search @elastic/workplace-search-frontend
+/x-pack/plugins/enterprise_search/server/saved_objects/workplace_search @elastic/workplace-search-frontend
 
 # Elasticsearch UI
 /src/plugins/dev_tools/ @elastic/es-ui