Merge 6 -> 7 as of pybind11 GaussMarkovProcess

[scpeters]

➡️ Forward port

Port ign-math6 to main as of #315.

Branch comparison: main...7717f49

Note to maintainers: Remember to Merge with commit (not squash-merge or rebase)

[codecov]

Codecov Report

Merging #379 (d0ed5be) into main (04028c9) will not change coverage.
The diff coverage is n/a.

❗ Current head d0ed5be differs from pull request most recent head 56b896c. Consider uploading reports for the commit 56b896c to get more accurate results

@@           Coverage Diff           @@
##             main     #379   +/-   ##
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  Coverage   99.63%   99.63%           
=======================================
  Files          65       65           
  Lines        6111     6111           
=======================================
  Hits         6089     6089           
  Misses         22       22           

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[ahcorde]

we have a warning related with Quaternion<int> I don't know if does make sense or not to have a class like this. Few can only represents with this class a few angles.

[scpeters]

we have a warning related with Quaternion<int> I don't know if does make sense or not to have a class like this. Few can only represents with this class a few angles.

I agree it doesn't make much sense, but it might be needed for Matrix3i due to the coupling between Matrix3 and Quaternion

I've cherry-picked the fix for the warning from part of #361