Implement user defined runtime zoom factor

[UrbanBobek]

Add a mechanism to apply a custom zoom factor for the runtime window.

The desired zoom factor can be set in settings.ini as:

org.csstudio.display.builder.runtime.app/default_zoom_factor=1.23

Refers to #3366

[kasemir]

Sorry, I missed that the first time around:

Can't the new default_zoom_factor be added to the existing
https://github.com/ControlSystemStudio/phoebus/blob/master/app/display/runtime/src/main/resources/display_runtime_preferences.properties
and associated
https://github.com/ControlSystemStudio/phoebus/blob/master/app/display/runtime/src/main/java/org/csstudio/display/builder/runtime/Preferences.java ?

Seems wrong to start a new preference file for what's just another runtime preference

[UrbanBobek]

Sorry, I missed that the first time around:

Can't the new default_zoom_factor be added to the existing https://github.com/ControlSystemStudio/phoebus/blob/master/app/display/runtime/src/main/resources/display_runtime_preferences.properties and associated https://github.com/ControlSystemStudio/phoebus/blob/master/app/display/runtime/src/main/java/org/csstudio/display/builder/runtime/Preferences.java ?

Seems wrong to start a new preference file for what's just another runtime preference

Good point, I didn't consider this during implementation. Fixed.