Sync View Angle GUI with view controller

[jennuine]

🎉 New feature

Requires gazebosim/gz-gui#506

Summary

Syncs the View Angle GUI when the view controller may be set elsewhere (e.g., in the plugin configuration)

Test it

1. Add <view_controller>ortho</view_controller> to:
   

   gz-sim/examples/worlds/minimal_scene.sdf

   Lines 30 to 46 in 7ba7377

   	<plugin filename="MinimalScene" name="3D View">
   	<ignition-gui>
   	<title>3D View</title>
   	<property type="bool" key="showTitleBar">false</property>
   	<property type="string" key="state">docked</property>
   	</ignition-gui>
   	<engine>ogre2</engine>
   	<scene>scene</scene>
   	<ambient_light>0.4 0.4 0.4</ambient_light>
   	<background_color>0.8 0.8 0.8</background_color>
   	<camera_pose>-6 0 6 0 0.5 0</camera_pose>
   	<camera_clip>
   	<near>0.25</near>
   	<far>25000</far>
   	</camera_clip>
   	</plugin>

2. Run:

ign gazebo /path/to/minimal_scene.sdf

3. Expand the View Angle plugin and you should see Orthographic View Control selected

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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