Improve test code to find VS root automatically

[pratikone]

Is your feature request related to a problem? Please describe.

Currently test code uses GetVsInstallRoot function to look at pre-defined locations to find Visual Studio installed location. This is not a generic solution.

Describe the solution you'd like

We need to use services like vswhere to find where VS is installed (and pick one if there are multiple copies).

The challenge in the solution is that we need to make changes for the CI pipeline to be aware of vswhere too. It would involve changing yaml files related to deployment.

Describe alternatives you've considered

Using vswhere is one way, there could be another way too.

Applies to the following platforms:

• [X] WinUI
• [X] WPF
• [X] UWP