fix(desktop): await execFilePromise and read stdout properly - #27499

@adamdotdevin @Brendonovich

Zed/VSCode now launchs without error. However:

1. Button gets stuck with a loading animation until the launched app is closed - this effectively prevents us from launching another app
2. Powershell is still not working. The target path is incorrectly passed:

powershell.exe C:\TEMP
C:\TEMP : The term 'C:\TEMP' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a
path was included, verify that the path is correct and try again.

Correct syntax:

powershell.exe -NoExit -Command "Set-Location 'C:\TEMP'"