Add support for nuget version 2 lock files

What does this MR do?

In this MR we introduce support for nuget lock files version 2. v2 is backwards compatible with v1 lock files. The changes that are introduced are the following:

• Update nuget parser to accept v1 and v2 lock files
• Update unit tests:
  • Wrong version file moved from v2 to v3
  • Add a unit test for a v2 lock file

What are the relevant issue numbers?

Add support for Version 2 of Nuget's packages.l... (gitlab-org/gitlab#398680 - closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer