[UI v2] chore: move artifact type.d.ts to just types.ts

[devinvillarosa]

Updates artifact type.d.ts to just types.ts

Found a good thread saying why this pattern isn't supported: microsoft/TypeScript#52593 (comment)

And a good video explanation: https://www.youtube.com/watch?v=zu-EgnbmcLY

Checklist

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