DebugConsole window does not take keyboard input

Summary:
In order to add more tabs which can further help monitoring how KWin
handles some aspects the DebugConsole is changed to not take keyboard
input. This means it can only be navigated using pointer device or touch
screen.

This is needed for adding a new tab to monitor clipboard changes. On
Wayland sometimes windows don't get the clipboard, so it would be
helpful to have a debug monitor to see when the clipboard changes. But
for that debug console window may not take keyboard events.

To support this DebugConsole sets the WA_ShowWithoutActivating attribute
which gets honored by the InternalWindowEventFilter and does not forward
key events to such windows.

Reviewers: KWin, Plasma on Wayland

Subscribers: plasma-devel, kwin

Tags: Plasma on Wayland, KWin

Differential Revision: https://phabricator.kde.org/D2620