Refactor the content provider test to remove external resources depedency

[leoporoli]

Background & motivation

Now our tests on git_package_content_provider_test depends on external repositories and these are susceptible to change or we are force to have online connection to run this unit test.

Desired behaviour

Remove the external resources dependency by providing a way to mock them.

How important is this to you?

Nice to have; this feature would make using Kurtosis more enjoyable.

What area of the product does this pertain to?

Other: anything not covered by the above