Add support for L8 and L16 image formats in WideAngleCameraSensor

[iche033]

🎉 New feature

Closes #479

Related PR: gazebosim/gz-rendering#1097

Summary

Added L8 and L16 type support.

Test it

You'll first need gazebosim/gz-rendering#1097

Then edit wide_angle_camera.sdf world in gz-sim, and add <format>L8</format> to the //model/link/sensor/camera/image tag, e.g.

diff --git a/examples/worlds/wide_angle_camera.sdf b/examples/worlds/wide_angle_camera.sdf
index 8482ae695..ce9c49c45 100644
--- a/examples/worlds/wide_angle_camera.sdf
+++ b/examples/worlds/wide_angle_camera.sdf
@@ -306,6 +306,7 @@
             <image>
               <width>800</width>
               <height>600</height>
+              <format>L8</format>
             </image>
             <clip>
               <near>0.1</near>

Run the example world to see the wide angle camera image in gray:

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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