Add system test for desktop shortcut (#12741)
The desktop shortcut, and the input gesture to activate it, do not have system tests
Use the input gesture to test the desktop shortcut.
Testing strategy:
Run: runsystemtests.bat -t "Starts from desktop shortcut" -v whichNVDA:installed
Confirmed that the test skips when running from source, eg: runsystemtests.bat -t "Starts from desktop shortcut"
