Implement all package uploads as feature tests

Summary

Follow-up of !33277 (merged).

In the above MR only maven and nuget uploads have been implemented as feature test.

To improve our code confidence, implements the following case as a similar feature test:

• PyPI upload
• Conan upload
• NPM upload (<- this in particular will not trigger the workhorse 🏓 )

For APIs that support path encoding, test those.

Improvements

• Code confidence improved
• More cases that tests multipart.rb

Risks

• None, the affected files are on the test side.

Involved components

Example of feature tests:

• spec/features/file_uploads/maven_package_spec.rb
• spec/features/file_uploads/nuget_package_spec.rb