Add pdk test unit graphical support

[isc-lindensc]

Summary of the new feature

Add graphical support for conducting and result review of unit tests similar to VS Code Test Explorer. So as a developer i can from VSCode run test and see the output in problems or directly highlighted in code, where a unit test has failed.

This should utilise features already available vi pdk test unit command to execute tests and report on issues based on selected Puppet version in VSCode.

[jpogran]

Thank you, this is a great feature request @isc-lindensc! This will take a bit of work to get right and it will require a few things to land before we can attempt this. I'll keep this ticket updated with progress