Allow host.id via IntakeV2 metadata

[JonasKunz]

Our universal profiling solution relies on the host.id field, which is already part of ECS and the OTel Semconv.
In order to improve correlation between the profiling solution and APM, we should store host.id on span and transaction documents too.

For the OTLP intake we already support receiving host.id as resource-attribute and store it on the span/transaction documents.

For intake-V2 host.id is never set (to my knowledge). We should add the ability to set the host.id via intake-v2 metadata payload.