This commit makes "Open in Windows Terminal" Context menu work again for
directory background even on system that OS fix is not applied.
This is a fallback solution to OS fixes mentioned in #6414.
While OS fix is on its way, we need a fallback that works on existing OS
versions.
The approach to this is: when no item is selected (nullptr for
IShellItemArray*), we use shell api to query the path of current active
Explorer window. A special case is handled for Windows Desktop. Once
we are able to obtain the path, we launch Windows Terminal with it.
## Validation Steps Performed
1. Right click on desktop to bring up the Context menu, pick "Open in
Windows Terminal", verify that a terminal is opened with correct
initial path.
2. Open a few File Explorer windows, pick any window, navigate to a
folder, click on "Background" to bring up the context menu, click
"Open in Windows Terminal" verify that a terminal is opened with
correct initial path.
Closes#6414
fcca88ab25