Accessibility: Welcome dialog order of controls is incorrect

[SteveL-MSFT]

Bugs

If this issue is a bug:

• Which version of WiX are you building with?

3.9.1208.0

• Which version of Visual Studio are you building with (if any)?

N/A

• Which version of the WiX Toolset Visual Studio Extension are you building with (if any)?

N/A

• Which version of .NET are you building with?

N/A

• If the problem occurs when installing your packages built with WiX, what is the version of Windows the package is running on?

N/A

• Describe the problem and the steps to reproduce it.

The default WiX welcome dialog has the controls in the wrong order when observed by Narrator Scan mode.

1. Start a MSI installer built from WiX that has the default Welcome Dialog
2. Start Narrator (Ctrl+Win+Enter)
3. Start Scan Mode (Insert+Space)
4. The `Next` button should be highlighted, press down to navigate to next control.
5. The `Cancel` button should be highlighted, press down again.
6. After this, the order is seemingly random.  Keep pressing down to navigate through the controls.

• Describe the behavior you expected and how it differed from the actual behavior.

Expectation is that the order is top to bottom and left to right. Otherwise, a visually impaired user cannot correctly determine the layout of the controls.

[barnson]

Which dialog set are you using? A screen shot or repro project would be helpful too.

[SteveL-MSFT]

https://github.com/PowerShell/PowerShell/blob/master/assets/Product.wxs