Improve voxel rendering by using multiple nodes instead of CompositeShape

[jslee02]

---

Before creating a pull request

• Document new methods and classes
• Format new code files using clang-format

Before merging a pull request

• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• Add unit test(s) for this change (N/A)

[codecov]

Codecov Report

Merging #1334 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #1334      +/-   ##
=========================================
+ Coverage   56.89%   56.9%   +0.01%     
=========================================
  Files         366     366              
  Lines       27167   27167              
=========================================
+ Hits        15457   15460       +3     
+ Misses      11710   11707       -3

Impacted Files	Coverage Δ
dart/dynamics/PointCloudShape.hpp	0% <ø> (ø)	⬆️
dart/dynamics/Skeleton.cpp	66.12% <0%> (+0.16%)	⬆️