Add IntelliSense for testing properties

[Youssef1313]

Fixes microsoft/testfx#4118

@Evangelink @nohwnd for review.

[Evangelink]

Global comments:

Some details like nuget packages, extensions included in profiles... are probably better not explained here but instead linked into doc so we could better handle changes and more complex details in the future.

You are sometimes wrapping values in single quotes sometimes not. It's probably better to always do it for property name, values and package names.

[YuliiaKovalova]

Is it needed for VS functionality only?

[Youssef1313]

Is it needed for VS functionality only?

@YuliiaKovalova Ideally, we want the completion to work fine everywhere. VS, VSCode, Rider. I have no idea if the XSD is respect only in VS or is respected everywhere. And if not respected everywhere, is there even a way to get it to work everywhere?

[rainersigwald]

Is it needed for VS functionality only?

Ideally, we want the completion to work fine everywhere. VS, VSCode, Rider. I have no idea if the XSD is respect only in VS or is respected everywhere. And if not respected everywhere, is there even a way to get it to work everywhere?

Today this only works in VS. Getting it to work everywhere is tracked by #1774.

[Youssef1313]

@rainersigwald This is green now. Is it good to merge please?

[rainersigwald]

@JanKrivanek I can't think of a reason not to take this to 17.13--is that still ok timeline-wise?

[Youssef1313]

@rainersigwald @YuliiaKovalova @JanKrivanek Is this good to merge?

[JanKrivanek]

It's good to go!

@Youssef1313 - did you have in mind any timeline of shipping this? Is early Feb with 17.14 Preview 1 fine?

[Youssef1313]

I haven't planned a timeline with @Evangelink on this. I think it should be fine early Feb, but will double check.

[Evangelink]

Sure, the earlier the better but this is absent for some time so it's not blocking anything. Thanks.