Source zip writer can only handle sources which are itself a zip file

[neubs-bsi]

This is copied from an internal repository. Original reporter: @maxhbr

See: https://github.com/eclipse/antenna/blob/55e9a0d9fb7243d0b8e3e0485b78fb3d7706891d/antenna-workflow-steps/generators/antenna-source-zip-generator/src/main/java/org/eclipse/sw360/antenna/workflow/generators/SourceZipWriter.java#L171

Plain text or .tar.gz are not supported.

Acceptance Criteria:

• Sources are handled as is, whatever is downloaded will be packed into the sources.zip
• No special handling of dedicated file types anymore
• Sources are structured in the file in an appropriate way, accepted by the PO

Comments from previous issue:
Suggestions from Refinement:

Do not unpack zip files at all
In the end, have a folder of sources and just zip this folder (which may contain zips, tar.gz, etc.)