Support polynomial piecewise scalar fields

[hidmic]

🎉 New feature

Summary

Spin-off from gazebosim/gz-sim#1357. This PR introduces a number of classes, namely:

• an Interval class for scalar intervals
• a Polynomial3 class for cubic polynomials
• a Region3 class for regions in R^3
• a SeparableScalarField3 class for separable scalar fields in R^3
• a PiecewiseScalarField3 class for piecewise scalar fields in R^3

to support polynomial piecewise scalar fields.

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]

Even though later commits build on top of previous ones, each one of them is fairly self-contained. If the size of the PR is beyond what reviewers feel willing to tackle, I can split this PR into multiple ones.

FYI @caguero.

[codecov]

Codecov Report

Merging #387 (43f8801) into main (0d05f47) will decrease coverage by 0.43%.
The diff coverage is 82.72%.

❗ Current head 43f8801 differs from pull request most recent head 4b319c7. Consider uploading reports for the commit 4b319c7 to get more accurate results

@@            Coverage Diff             @@
##             main     #387      +/-   ##
==========================================
- Coverage   99.64%   99.20%   -0.44%     
==========================================
  Files          65       70       +5     
  Lines        6115     6311     +196     
==========================================
+ Hits         6093     6261     +168     
- Misses         22       50      +28     

Impacted Files	Coverage Δ
include/ignition/math/PiecewiseScalarField3.hh	75.00% <75.00%> (ø)
include/ignition/math/Interval.hh	77.04% <77.04%> (ø)
include/ignition/math/Polynomial3.hh	85.71% <85.71%> (ø)
include/ignition/math/Region3.hh	92.30% <92.30%> (ø)
...e/ignition/math/AdditivelySeparableScalarField3.hh	94.73% <94.73%> (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%)	⬆️
... and 2 more

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[hidmic]

I can't see coverage reports, but a few classes definitely could use more unit tests.

[hidmic]

As per f2f chat, I'll be improving test coverage and splitting each commit in this PR into its own PR.

[hidmic]

Superseded by #388, #390, #397, and #398.