Change namespace of metadata fields that can cause confusion

The agent automatically fills fields such as `cloud.account.id`. This is normally fine but with some integrations e.g.: `gcp`, `aws` it can be confusing since they also make use of the `cloud.*` fields, which can lead to a mix of inconsistent information i.e. `cloud.account.id` belongs to the agent host and `cloud.project.name` is populated from the integration.

Would be useful to consider changing fields automatically populated by the agent to something that can't be confused and which meaning is deterministic across integrations (for example leveraging https://www.elastic.co/guide/en/ecs/current/ecs-cloud.html#_field_reuse_3).

This could also happen with `orchestrator.*` fields.