win32: add fallback to environment vars for system folder

[kasperk81]

Implement fallback to environment variables for system folders in NanoServer, ensuring correct paths when SHGetKnownFolderPath fails.

in base nanoserver image, all values are returning empty

foreach (Environment.SpecialFolder folder in Enum.GetValues(typeof(Environment.SpecialFolder)))
{
    Console.WriteLine($"{folder}: {Environment.GetFolderPath(folder)}")
}

both SHGetFolderPathW and SHGetKnownFolderPath fail with error -2147467259.

environment variables in the base image:
docker run --rm mcr.microsoft.com/windows/nanoserver:ltsc2022 cmd /c "set"

ALLUSERSPROFILE=C:\ProgramData
APPDATA=C:\Users\ContainerUser\AppData\Roaming
CommonProgramFiles=C:\Program Files\Common Files
CommonProgramFiles(x86)=C:\Program Files (x86)\Common Files
CommonProgramW6432=C:\Program Files\Common Files
COMPUTERNAME=594228B8A3DC
ComSpec=C:\Windows\system32\cmd.exe
DriverData=C:\Windows\System32\Drivers\DriverData
LOCALAPPDATA=C:\Users\ContainerUser\AppData\Local
NUMBER_OF_PROCESSORS=4
OS=Windows_NT
Path=C:\Windows\system32;C:\Windows;
PATHEXT=.COM;.EXE;.BAT;.CMD
PROCESSOR_ARCHITECTURE=AMD64
PROCESSOR_IDENTIFIER=AMD64 Family 25 Model 1 Stepping 1, AuthenticAMD
PROCESSOR_LEVEL=25
PROCESSOR_REVISION=0101
ProgramData=C:\ProgramData
ProgramFiles=C:\Program Files
ProgramFiles(x86)=C:\Program Files (x86)
ProgramW6432=C:\Program Files
PROMPT=$P$G
PUBLIC=C:\Users\Public
SystemDrive=C:
SystemRoot=C:\Windows
TEMP=C:\Windows\TEMP
TMP=C:\Windows\TEMP
USERDOMAIN=User Manager
USERNAME=ContainerUser
USERPROFILE=C:\Users\ContainerUser
windir=C:\Windows

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[kasperk81]

@ViktorHofer @akoeplinger I removed this condition, and it's now passing where it was failing before: link to comment. I didn’t update other environment tests since they compare values against win32 SHGetFolderPathW, which returns a general error (-2147467259) on nano server

[kasperk81]

@jkotas analysis shows same error as #108210 but it's not a tracking issue
(this is win32 only change)

[jkotas]

I am leaving it to @dotnet/area-system-runtime owners to do the final signoff and merge.

[ViktorHofer]

gentle ping @dotnet/area-system-runtime

[rhuijben]

This function is part of the shell experience, so desktop only. So I'm not surprised that it fails on systems without shell. This will probably also fix usages in system services, etc. And probably everything else where no user registry hives are loaded.