Add Interval class

[hidmic]

🎉 New feature

Summary

Split from #387. This PR introduces an Interval class to represent scalar, real intervals.

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 and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[hidmic]

@chapulina PTAL!

[ahcorde]

Do you mind to add this a Python interfaces ? or if you don't have time please open an issue.

[codecov]

Codecov Report

Merging #388 (2adb728) into main (0d05f47) will increase coverage by 0.08%.
The diff coverage is 100.00%.

❗ Current head 2adb728 differs from pull request most recent head b6fbc87. Consider uploading reports for the commit b6fbc87 to get more accurate results

@@            Coverage Diff             @@
##             main     #388      +/-   ##
==========================================
+ Coverage   99.64%   99.72%   +0.08%     
==========================================
  Files          65       66       +1     
  Lines        6115     6189      +74     
==========================================
+ Hits         6093     6172      +79     
+ Misses         22       17       -5     

Impacted Files	Coverage Δ
include/ignition/math/Interval.hh	100.00% <100.00%> (ø)
include/ignition/math/Plane.hh	100.00% <0.00%> (ø)
include/ignition/math/Matrix4.hh	100.00% <0.00%> (ø)
include/ignition/math/Inertial.hh	100.00% <0.00%> (ø)
include/ignition/math/MassMatrix3.hh	99.39% <0.00%> (+<0.01%)	⬆️
include/ignition/math/Quaternion.hh	100.00% <0.00%> (+0.24%)	⬆️
include/ignition/math/Helpers.hh	100.00% <0.00%> (+0.69%)	⬆️
src/Helpers.cc	98.21% <0.00%> (+2.67%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ebd1a13...b6fbc87. Read the comment docs.

[hidmic]

Do you mind to add this a Python interfaces ? or if you don't have time please open an issue.

@ahcorde I'll open an issue once we merge this PR. I promise I'll get back and implement pybind11 bindings later on, but I need this feature in ASAP.

[chapulina]

This looks great, thanks for the tests, documentation and example. I just have minor comments, but nothing blocking.

Python interfaces will be added on follow up PRs.

[scpeters]

there may be some issues with static initialization of this variable (see #269). It looks like this is almost following the pattern from #283, but it is not a constexpr, so I think some additional work will be needed