Changes

NEWT: MonitorDevice: Add monitor-name, maybe an empty string. Implemented for X11 and Windows for now.

NEWT Screen: Cleanup get*Monitor*() methods

NEWT MonitorDevice: Fix pixelScale storage, own float[2], don't reuse given object

NEWT X11: Fix positionChanged: We need to translate the 0/0 client position to the root window (global screen) ..

.. otherwise, we might end up receiving a client position of 0/0, while being positioned in a different absolute place within root.

NEWT Soft-PixelScale (p7): get{Global->}PixelScaleEnv(..): Support per monitor values w/ QT_SCREEN_SCALE_FACTORS syntax, use for X11

Per-monitor values are parsed if value is not a float and stored
in a given Map<String,float[2]>, parallel to a detected global_pixel_scale_xy.

The per-monitor value syntax matches QT_SCREEN_SCALE_FACTORS,
i.e. the regular expression '(<string>=<float>;)+',
e.g. QT_SCREEN_SCALE_FACTORS='DP-1=1.25;DP-2=1.25;HDMI-1=1.25;'

The per-monitor value is preferred and on X11 stored within the MonitorDevice,
matching the MonitorDevice's name.

The following env-var names are searched on X11:
   "QT_SCREEN_SCALE_FACTORS", "QT_SCALE_FACTOR", "GDK_SCALE", "SOFT_SCALE"