MSIX: Runtime layering for modification package when not VFS

[Tim Mangan]

With the fixes in 1903, I can create a package with Notepad++, and then create a Modification Package to it that adds a plug-in dll.  That is, I can do this and it works as long as I do not specify the installation folder while packaging.

But Notepad++ needs me to use the PSF in order for Notepad++ to see the customized configuration file (which is in the user's appdata area; without the PSF to perform a copy on access to the file it can't see the file).  To use the PSF I must specify the installation folder while packaging or else the PsfLauncher won't see the config.json file as it must be placed at the root of the package and I can only do that if I specify the installation folder in the packaging tool dialog.  Specifying this folder in both packages, the app does not see the plugin when I deploy the two packages.

I believe the fix added to 1903 is incomplete and needs to include this use case.  Entered in feedbackhub with case https://aka.ms/AA5iy0i 

[#2]

@Tim Mangan, for modification packages we scoped it to only work with folders that are VFS. We are looking into perhaps extending it to folders that are not VFS but at this time there is no plans to do so. 

[#3]

@Dian Hartono I would suggest that this limitation heavily impacts a key feature benefit of MSIX - that of separation of enterprise configuration.