When scanning a Docker image also report it as its own package

An image contains package-like data such as these, and we should create a Discovered Package record from these:

``` labels:
org.label-schema.url: https://www.elastic.co/products/elasticsearch
org.label-schema.name: Elasticsearch
org.label-schema.usage: https://www.elastic.co/guide/en/elasticsearch/reference/index.html
org.label-schema.vendor: Elastic
org.label-schema.license: Apache-2.0
org.label-schema.vcs-ref: 747e1cc71def077253878a59143c1f785afa92b9
org.label-schema.vcs-url: https://github.com/elastic/elasticsearch
org.label-schema.version: 7.10.2
org.label-schema.build-date: '2021-01-13T00:42:12.435326Z'
org.opencontainers.image.url: https://www.elastic.co/products/elasticsearch
org.opencontainers.image.title: Elasticsearch
org.label-schema.schema-version: '1.0'
org.opencontainers.image.source: https://github.com/elastic/elasticsearch
org.opencontainers.image.vendor: Elastic
org.opencontainers.image.created: '2021-01-13T00:42:12.435326Z'
org.opencontainers.image.version: 7.10.2
org.opencontainers.image.licenses: Apache-2.0
org.opencontainers.image.revision: 747e1cc71def077253878a59143c1f785afa92b9
org.opencontainers.image.documentation: https://www.elastic.co/guide/en/elasticsearch/reference
```