De-duplicate our WinUI2/3 workflow definitions with a matrix

[michael-hawker]

Fixes #299

Changes:

• Uses a matrix to have a single workflow that both runs our WinUI 2 and WinUI 3 build pass
  • Only calls the one step difference for WinUI 3 on the WinUI 3 matrix pass
• Updates XAML Styler to version compatible with .NET 6 so we remove .NET Core 3 from our build process
• Updates GitHub Actions to latest versions
• Updates to using latest revision of .NET 6 SDK automatically
• Ensures test reports are only attempted to be uploaded if a test step was completed

Will move other updates to another PR, we need to update the WASM head to be off .NET 5 and maybe fix some other things, same things that are tripping up the #183 PR on linux as well.

[michael-hawker]

Hmm, so the split matrix work, but the new condition for uploading the test results failed... was a bit hard to find documentation on how those status things work.

[michael-hawker]

Ah, found docs here I was missing: https://docs.github.com/en/actions/learn-github-actions/contexts#steps-context

I want conclusion not status.

[michael-hawker]

Test reports are uploaded now as well:

(Need to figure out later how to better bucket since we run tests twice in each environment, but that can be a separate thing. Testspace Docs here)

[Arlodotexe]

Very neat! I don't spot any issues, good to merge 👍

[michael-hawker]

Thanks @Arlodotexe, updated the branch protection rules to look for the new job names. So, just remember to rebase/update any PRs as you make changes. FYI @niels9001 as well for his open PR.