[Build] Additional files on test projects

[javiercn]

There's a bunch of additional files that get linked in on tests projects at the root folder (note the above is an empty project). It's not clear to me why they need to be there at all, so I would suggest we remove them. If for some reason that's not possible, we should at least put them in a single folder where they don't get in the way.

The current experience is quire jarring

[dougbu]

Looks like the relevant item groups have a Visible="false" option that should hide them in Visual Studio. Would that be sufficient @javiercn❔

[dougbu]

And, to clarify: You're not interested in removing the files -- just in hiding them❔