Replace deprecated Vitest workspace with config

[MaxAtoms]

Cf. https://vitest.dev/blog/vitest-3-2.html#workspace-is-deprecated

[MaxAtoms]

I think this main Vitest config is only relevant when running tests from the IDE or via npx vitest, right?
Our npm run-scripts directly reference the sub-configs

[EagleoutIce]

Is it deprecated? yes. Does it harm modern systems? afaik no.
But @gigalasr and others reported problems with vite without having a fallback workspace to work on! So please recheck @gigalasr or add to this

[EagleoutIce]

And even though we use npm runs, people still want to use the IDE runners, but let's have the people with problems (maybe @Ellpeck was one of them) have a look at this and see whether this also resolves the problem.

But given that it apprently works for you @MaxAtoms maybe it works for the others too :D

[MaxAtoms]

My commit message might have been a bit confusing 😬 This is not removing the settings from the workspace file, but rather replace them with a configuration that is compatible with Vitest 4.
The behavior should be the same as far as my testing goes.

[EagleoutIce]

Jeah sorry I've seen that when looking at the changes too, but I would still want the others to check (at least @gigalasr) to see whether it works with the new format!

[gigalasr]

On this branch I get the following error when opening the project in vscode:

[gigalasr]

Actually after updating and restarting the extension and vscode, and reinstalling all node modules the problem is gone :D

[EagleoutIce]

allright this is mergeable then :D