Set collision detector and solver for DART

[chapulina]

🎉 New feature

Summary

Add a feature that allows setting and getting a couple of physics options: the collision detector and the solver. DART offers a few options for each of these. The motivation is to make it easier for end users to test different options (which I want to do on #218).

It can be seen on the commit history that my first implementation was getting the options directly from SDF files. However, the sdf::World object received from ign-gazebo doesn't contain the Element() pointer, and the sdf::Physics object doesn't have collision detector and solver information yet due to gazebosim/sdformat#508. That's why I went for the feature approach instead.

Test it

The API's usage can be seen on the added test. It's also used on gazebosim/gz-sim#684.

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

Note to maintainers: Remember to use Squash-Merge

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[codecov]

Codecov Report

Merging #225 (dde6786) into main (f3342ee) will increase coverage by 0.06%.
The diff coverage is 86.88%.

@@            Coverage Diff             @@
##             main     #225      +/-   ##
==========================================
+ Coverage   82.22%   82.28%   +0.06%     
==========================================
  Files         107      109       +2     
  Lines        4292     4353      +61     
==========================================
+ Hits         3529     3582      +53     
- Misses        763      771       +8     

Impacted Files	Coverage Δ
dartsim/src/plugin.cc	100.00% <ø> (ø)
dartsim/src/WorldFeatures.cc	82.97% <82.97%> (ø)
include/ignition/physics/detail/World.hh	100.00% <100.00%> (ø)

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[scpeters]

@osrf-jenkins run tests please

[azeey]

Looks great! Just a few minor comments.