Add testing platform architecture

[Evangelink]

Summary

Move and reorganize the architecture/extensibility documentation for the new testing platform.

cc @MarcoRossignoli

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Internal previews

📄 File	🔗 Preview link
docs/core/testing/unit-testing-platform-architecture-capabilities.md	docs/core/testing/unit-testing-platform-architecture-capabilities
docs/core/testing/unit-testing-platform-architecture-extensions.md	docs/core/testing/unit-testing-platform-architecture-extensions
docs/core/testing/unit-testing-platform-architecture-services.md	docs/core/testing/unit-testing-platform-architecture-services
docs/core/testing/unit-testing-platform-architecture.md	docs/core/testing/unit-testing-platform-architecture
docs/core/testing/unit-testing-platform-exit-codes.md	docs/core/testing/unit-testing-platform-exit-codes
docs/core/testing/unit-testing-platform-intro.md	docs/core/testing/unit-testing-platform-intro

[MarcoRossignoli]

I don't see the image and the mermaid rendering correctly is it related only to the "preview"?

[Evangelink]

@IEvangelist Are our docs supporting mermaid?

[IEvangelist]

I'm still not done with this review, it's taking a really long time - been working on it for a while now. I'm going to comment on it, and return when I can focus a bit more. But for now, here's what I have.

[Evangelink]

I'm still not done with this review, it's taking a really long time - been working on it for a while now.

Thank you so much for everything you have reviewed already! We know this is a super big change, I have read it a few times and I am still not 100% happy with the results of what we wrote nor the structure but it's not always easy to get the abstraction of knowing all the implementation details.

[IEvangelist]

There are still a few things that we'll need to update, this is starting to shape up though. Let's consider this 2/3 in terms of reviews. 🤓

[IEvangelist]

I've checked back on this one a few times, there's still a lot of suggestions that haven't been resolved. I'll come back once those are addressed. /cc @Evangelink

[Evangelink]

@IEvangelist Yes sorry! I have been pretty busy with other priorities, I'll get back here early next week!

[IEvangelist]

@IEvangelist Yes sorry! I have been pretty busy with other priorities, I'll get back here early next week!

No worries, I completely understand. I just wanted to make sure I wasn't missing anything. I'm off all next week, so I'll check back the week of 8/12. Thank you, my friend! @Evangelink

[Evangelink]

Hey @IEvangelist, could we resume work on this PR? We have finished integration with xUnit v3, NUnit, and we are getting close to finishing with F# Expecto.

[Evangelink]

@IEvangelist Could we resume work on this PR when you have some time? I think I have handled all the comments you made to me.

[IEvangelist]

We need to address the build warnings, see here. Then, let's ensure that all the images are cropped nicely, then we should be able to merge.

[Evangelink]

@IEvangelist PR is green :) A HUGE thank you for your support through this massive update.