VCIO-next: VulnerableCode: Use proper apk package type for Alpine

[pombredanne]

Today we use:

• pkg:alpine/gcc@9.3.0-r0?arch=aarch64&distroversion=v3.11&reponame=main
  And this is invalid according to the PURL spec, but the spec was changed somehow.
  See:
• Contradicting namespace case requirement for apk package-url/purl-spec#219

[keshav-space]

This is now completed in #1739
To test this search some alpine package like pkg:apk/alpine/gcc in https://public.vulnerablecode.io/packages/search