Eigen 5.0 release next door

[stefano2734]

See milestones at gitlab with many bugfixes.

all issues are done.
Only release issue todo.

https://gitlab.com/libeigen/eigen/-/milestones/10#tab-issues

https://gitlab.com/libeigen/eigen/-/milestones

https://gitlab.com/libeigen/eigen/-/issues/2907
https://gist.github.com/SteveBronder/aa19ff60c02ac02de9399d056f730da6