Add test cases & renovate to `dotnet-basic` sample

[michael-valdron]

Which area is this issue related to?

/area ci
/area registry

Issue Description

We need to add test cases and renovate automation to dotnet-basic to ensure this sample is both patched and tested for use by devfile registry sample consumers.

Acceptance Criteria

• Add test cases to ensure sample can still be parsed and used by consumers
• Add renovate configuration to be picked up by organization renovate bot