Removes the server side deps for metrics and entities (elastic#120412)

## Summary

See: elastic#110903

This removes all the top level API `export *` spots from:
* `metrics_entities` plugin within the server section

This reduces the number of metrics and warning about undocumented functions.

In the file `metrics_entites/server/index.ts` I now put the advice of:

```
// Careful of exporting anything from this file as any file(s) you export here will cause your functions to be exposed as public.
// If you're using functions/types/etc... internally or within integration tests it's best to import directly from their paths
// than expose the functions/types/etc... here. You should _only_ expose functions/types/etc... that need to be shared with other plugins here.
// When you do have to add things here you might want to consider creating a package such to share with other plugins instead as packages
// are easier to break down.
// See: https://docs.elastic.dev/kibana-dev-docs/key-concepts/platform-intro#public-plugin-api
```

x-pack/plugins/metrics_entities/common/index.ts

@@ -5,10 +5,9 @@
  * 2.0.
  */
 
-// TODO: https://github.com/elastic/kibana/issues/110904
-/* eslint-disable @kbn/eslint/no_export_all */
-
-export const PLUGIN_ID = 'metricsEntities';
-export const PLUGIN_NAME = 'metrics_entities';
-
-export * from './constants';
+// Careful of exporting anything from this file as any file(s) you export here will cause your functions to be exposed as public.
+// If you're using functions/types/etc... internally or within integration tests it's best to import directly from their paths
+// than expose the functions/types/etc... here. You should _only_ expose functions/types/etc... that need to be shared with other plugins here.
+// When you do have to add things here you might want to consider creating a package such to share with other plugins instead as packages
+// are easier to break down.
+// See: https://docs.elastic.dev/kibana-dev-docs/key-concepts/platform-intro#public-plugin-api

x-pack/plugins/metrics_entities/server/services/utils/compute_transform_id.ts

@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-import { ELASTIC_NAME } from '../../../common';
+import { ELASTIC_NAME } from '../../../common/constants';
 
 export const computeTransformId = ({
   prefix,