Enable Global Labels for RUM Agents in APM

Issues with global labels being stripped for RUM agents, causing problems with setting permissions and aggregating metrics based on for e.g.: `yoda.id` which is used to provide access to the users.

The global label is being removed from the pre-aggregated data streams `metrics-apm*` of APM, but present in the `traces-apm*` indices. The global labels(`yoda.id`) which is being removed for rum-agents and therefore unable to set permissions which is based on this ID and hence users are no longer able to see aggregated metrics for their services.

Need a solution to enable global labels for RUM agents without violating naming standards or causing high cardinality issues.