This commit adds a fallback mechanism if the OS doesn't send a DPI change
as expected. When the process is started with System DPI awareness and
only the thread is PerMonitorV2 aware, there are some scenarios, when the
OS does not send a DPI change event when a child Shell is positioned and
opened on another monitor as its parent Shell. To work around that limitation
a check is added to Shell::WM_WINDOWPOSCHANGED to trigger a dpi change
event if an unexpected DPI value is detected.