enable Blender addon with Python

To enable a Blender add-on with Python, use

import addon_utils
addon_utils.enable(addon_name)

Don’t use this outdated code

import bpy
bpy.ops.preferences.addon_enable(module=addon_name)

Since this will fail if the addon folder didn’t exist on Blender start up.
It also uses operators which can cause issues when run from Qt.