Replace XCTests with Swift Testing

[dl-alexandre]

There was trouble in running the tests, something with the schemes on my end. Only could run on scheme ignite-package, though they'd crash.

[dl-alexandre]

Also PublishingContext required changes because of missing from: argument, plus extra root: argument

[twostraws]

Hello! Thank you for this contribution. Why are we moving to Swift Testing?

[dl-alexandre]

A Swift Testing move isn't the wrong idea. A couple tests in this repo were some of my earliest testing attempts using XCTest. Learning Swift Testing has been more intuitive than working with XCTest. Plus, providing functional examples. For me, functional examples are the primer for understanding or reference new practices better. Given that this repo is still in development phases, implementing Swift Testing as its standard isn't a heavy lift. Hopefully this clarifies this, even if somewhat opinionated.

[twostraws]

I understand you might find it easier to learn Swift Testing, but there are much better ways to learn it than adopting it in a public project, and it would also cut us off from the many thousands of people who already use XCTest. While I could understand moving to Swift Testing once it has gained more traction, right now it has a really tiny percentage share of usage in the Swift world, so I'd rather stay away from it here for the time being.

[dl-alexandre]

Here's a split testing commit, let me know if you'd like that changed.

[twostraws]

Unless I'm reading it wrong, this still seems to be bringing Swift Testing into the project, which again is not something I would support at this time.