[detectors/openstack] Contribute openstack/nova detector from resourcedetectionprocessor

[paulojmdias]

Problem Statement

collector-contrib/processor/resourcedetectionprocessor/internal/openstack/nova implements a resource detector for OpenStack Nova compute instances. There is currently no equivalent in go-contrib/detectors/, which means OpenStack detection is only available to collector-contrib pipelines and not to any Go SDK user.

Proposed Solution

Add a new detectors/openstack package implementing the OpenStack Nova detector as a resource.Detector, ported from the collector-contrib implementation, so that collector-contrib/processor/resourcedetectionprocessor can delegate to it and any other Go SDK user can adopt it.

Prior Art

• Collector-contrib implementation to port from: processor/resourcedetectionprocessor/internal/openstack/nova
• Tracking issue: [processor/resourcedetection] Align detectors with opentelemetry-go SDK detectors opentelemetry-collector-contrib#48159

Additional Context

What the collector-contrib detector does:

• Queries the OpenStack Nova Instance Metadata API.
• Emits: cloud.provider (openstack), cloud.platform (openstack_nova), cloud.region, host.id, host.name, host.type, host.image.id, host.image.name.