Improve cargo package detection support

[AyanSinhaMahapatra]

Improvements and bugfixes:

• Fix for parser crashing on cargo workspaces
• Fix a bug in dependency parsing (we were not returning any dependencies)
• Also support getting dependency versions from workspace
• Support more attributes from cargo
• Better handle workspace data thorugh extra_data ({workspace = true} would not be seen anymore even on parser failing)
• clean up workspace data from extra data on resolution

Reference: #3769

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📑 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR
  Run tests locally to check for errors.
• Commits are in uniquely-named feature branch and has no merge conflicts 📁
• Updated documentation pages (if applicable)
• Updated CHANGELOG.rst (if applicable)

[pombredanne]

LGTM! great. Just need a changelog

[AyanSinhaMahapatra]

Thanks @pombredanne , added CHANGELOG, now merging!