Send host.id received from profiler via IntakeV2 metadata

The universal profiling feature requires the `host.id` to be set for providing accurate CO2 and cost estimates.
For this reason, the profiling host agent sends the `host.id` via the domain socket to the apm-agent.

In addition https://github.com/elastic/apm-data/pull/246 added support for receiving the `host.id` via IntakeV2 metadata.
Therefore we should take the `host.id` received from the profiler and send it as metadata.

Note that the profiler might initiate the correlation a while after the agent has already started. Therefore we will need to be able update the cached metadata to include the `host.id`.