Lets start with fully encapsulating the `Repository` in the wrapper.
We should only consider making it a part of the public interface if
we start exposing too many `Repository` methods.

The bulk of this commit is changing tests so they can handle not having
access to the rawRepository.

And add integration tests which use actual running extension to validate
that we can select the repositories. The new methods have the same
purpose as the now-deprecated `getCurrentWorkspaceFolder` and
`getCurrentWorkspaceFolderOrSelectOne`.

This will enable us to attach logic to repositories in the future.
For example, we'll add GitLab API service to each repository to simplify
how we call API.