Remove ContextMenu from logical tree.
Remove ContextMenu from logical tree.

When the `ContextMenu` is not attached to a control, i.e. it is shown using `Show(control)` then we need to detach it from the logical tree once hidden otherwise it will leak, causing #3738.

SuperJMN/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Perspex,wieslawsoltes/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,grokys/Perspex,AvaloniaUI/Avalonia,grokys/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,Perspex/Perspex,AvaloniaUI/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,akrisiun/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,Perspex/Perspex