Since the changes of 6ae7aa4443, the
windows were shown when their geometry was restored as a side effect of
calling ::SetWindowPlacement(). This was unexpected and resulted in
flicker on startup, so fix this by explicitly passing SW_HIDE to
SetWindowPlacement() if the window is currently hidden and storing the
real show command inside wxTLW itself, where it will be used when it's
finally shown.
Save both the normal window geometry and its maximized position instead
of saving just its current position. This fixes restoring geometry of
the maximized windows as previously they were always restored on the
primary monitor, as their original position was lost.
Use the native {Get,Set}WindowPlacement() functions for a MSW-specific
wxTLWGeometry implementation to achieve this.
Closes#16335.
