[Build] Create Separate Jobs for UI Tests

[michael-hawker]

Describe the problem this feature would solve

It'd be nice if we could separate out our UI Tests (and possibly Unit Tests) to run as secondary jobs in the CI. For the UI Tests, this would run them more like an actual application, and as that suite grows help run things in parallel.

Describe the solution

Be able to run UI Tests separately in CI.

Additional context & Screenshots

The problem is currently that the UI Tests are built along with the main project, so they'd need to be separated out in for building alone by the cake script in the UITest Task. This means we probably need a separate solution to bundle them???

However, we still want them visible and runnable from the main solution for folks cloning the Toolkit. This means we probably need slightly separate configurations. We also need to be able to have a switch in the UI Test app project to use Project References locally, but then PackageReferences when running in the CI. Not sure if the TF_BUILD flag is enough?

@azchohfi having some notes for our Wiki about how all the build process works between management from the YAML to the actual building of bits and running of tasks via cake works would be handy. And the difference between the pipeline and release stages. Especially knowing more about how the solution file dictates what's actually built in the CI. Think that's something you could write up a page on? CommunityToolkit/WindowsCommunityToolkit-wiki#2

Hello, 'michael-hawker! Thanks for submitting a new feature request. I've automatically added a vote 👍 reaction to help get things started. Other community members can vote to help us prioritize this feature in the future!