APM agent settings telemetry.agent.global_labels.* should not be passed on to server

[mosche]

In APMJvmOptions, nested telemetry.agent.global_labels.* are flattened into a single telemetry.agent.global_labels setting as used by the agent. The previous telemetry.agent.global_labels.* settings are not recognized by the agent and should not be included in ServerArgs.
Due to the way APMJvmOptions depends on ServerArgs it's currently not trivial to exclude settings from ServerArgs based on filtering done for JVM options.

Currently this requires a workaround in APMAgentSettings to ignore any setting matching telemetry.agent.global_labels.*

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)