add bounding box sensor API stubs

[adlarkin]

Summary

I've added the public API for a bounding box sensor. Most of this is copy/pasted from #334, with a few changes:

1. There's only one constructor for the rendering::BoundingBox struct, which takes a type and label argument
2. The rendering::BoundingBoxCamera::DrawBoundingBox method takes the box color as an argument instead of defaulting to green

This PR just covers the breaking changes that are needed for the bounding box sensor so that we can add #334 to Fortress in a minor release. Some of the things I added here may not be breaking, but I wasn't sure, so I added whatever I thought could be ABI breaking. See #334 for an ogre2 implementation.

Test it

No tests have been added here because tests are written for this in #334

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[adlarkin]

I'd like some feedback on an API decision I made before this gets merged. See my comment below.

[codecov]

Codecov Report

Merging #420 (b10fea7) into main (5bf8dc6) will decrease coverage by 0.06%.
The diff coverage is 15.15%.

@@            Coverage Diff             @@
##             main     #420      +/-   ##
==========================================
- Coverage   55.18%   55.12%   -0.07%     
==========================================
  Files         191      192       +1     
  Lines       19348    19381      +33     
==========================================
+ Hits        10678    10683       +5     
- Misses       8670     8698      +28     

Impacted Files	Coverage Δ
include/ignition/rendering/Scene.hh	0.00% <ø> (ø)
include/ignition/rendering/base/BaseScene.hh	0.00% <0.00%> (ø)
src/PixelFormat.cc	73.33% <ø> (ø)
src/base/BaseScene.cc	73.91% <0.00%> (-1.42%)	⬇️
src/BoundingBox.cc	31.25% <31.25%> (ø)

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[chapulina]

Let's also add the dependency on ign-math eigen. It's best not to add dependencies to stable versions.

[adlarkin]

Let's also add the dependency on ign-math eigen

Added in 98a7bf1. I'm assuming that the ogre2 component can be updated in #334 since that's a plugin, right? Here's what I am referring to in #334: https://github.com/ignitionrobotics/ign-rendering/blob/4162fd7b95969691d6ef4918d795172a66e3053a/ogre2/src/CMakeLists.txt#L38

[chapulina]

I hope that's all we need 🤞