Monitor-specific scaling needs to be activated before the display that
is supposed to run in that mode is created. Currently, the scaling is
activated in the Workbench based on an according preference after the
Display has already been created.

This change moves the evaluation of the experimental preference and the
according initialization of monitor-specific scaling to before the
Display is created inside the Workbench. Since the preference is now
accessed at a point in time where no workspace may already be available,
the preference was moved to the ConfigurationScope so that it is stored
independent from the actual workspace.