naming convention for downloadhandlers

[hilmarf]

Description

The current names are:

ocm ocm-downloadhandlers | grep '^    - «' | sort
    - «helm/artifact»: download helm chart
    - «landscaper/blueprint»: uploading an OCI artifact to an OCI registry
    - «oci/artifact»: downloading an OCI artifact
    - «ocm/dirtree»: downloading directory tree-like resources
    - «plugin»: [downloaders provided by plugins]

this should be aligned with the uploadhandlers #288 and has to make sense together with the accessmethods and input types.

Done Criteria

• Result matches final proposal: https://github.com/open-component-model/internal-processes/pull/14
• Code has been reviewed by other team members
• Internal technical Documentation created/updated
• New / changed code is documented
• Analysis of existing tests (Unit and Integration)
• Unit Tests created for new code or existing Unit Tests updated
• Integration Test Suite updated (includes deletion of existing unnecessary Integration Test and/or creation of new ones if required)
• Enduser Documentation updated (if applicable)
• Successful demonstration in Review

[hilmarf]

keep it consistent with:

ocm ocm-accessmethods | grep '  - Access type' | sort -f
  - Access type «gitHub»
  - Access type «helm»
  - Access type «localBlob»
  - Access type «maven»
  - Access type «none»
  - Access type «npm»
  - Access type «ociArtifact»
  - Access type «ociBlob»
  - Access type «ocm»
  - Access type «S3»
  - Access type «s3»
  - Access type «wget»