Expand the test conditions for all package managers

Proposal

For all the existing package registries that have a group or instance level, update the related specs to test these extended conditions:

• Getting a package located in group/project (mainly tested)
• Getting a package located in user_namespace/project with different visibilities for user_namespace
• Getting a package located in root_group/subgroup/project with different visibilities for root_group and different visibilities for subgroup.

The impacted package managers are:

• Maven (instance and group level)
• Nuget (group level)
• npm (instance level)
• conan (instance level)
• composer (group level)

I would suggest grouping the changes by package type. So this issue could be implemented in 5 MRs.