If importing a project failed because its exist, ask the user to open/jump to the project

Consider the following situation:

1. One has imported a project `X` in the project but closed it
2. No one uses the Wizard "Import existing projects" or right click in the Git Repositories View and choose "Import Projects ...)
3. Try to import project `X` and get an error that it is already imported

This has bad user experience as the user obviously would not have tried to import it if he was aware of that fact and the dialog does not really help here.

Instead there should be the following options:

1. The project is open, then ask the user to jump to the project (e.g. in Package/Project Explorer)
2. If the project is closed, ask the user to open the project