Re-enable start from desktop shortcut test (#18582)
Closes #14293
Summary of the issue:
The system test 'Starts from desktop shortcut' as part of the 'Basic
start and exit tests' defined in startupShutdownNVDA.robot relied on
NVDA to be running to send the keyboard shortcut which is intended to
start NVDA.
As such it was flakey and disabled.
Description of user facing changes:
none
Description of developer facing changes:
none
Description of development approach:
call keyevents directly rather than through NVDA
