Bugfic: Curved geometries

[sandro-elsweijer]

Closes #2074

Describe your changes here:
I am so sorry for the diff count. But a huge part of this PR is documentation.
Fixes a bug in our curved mesh algorithms in which in some edge cases geometries were either not linked to tree faces or they were linked with wrong parameters. This can be observed by executing the curved mesh tutorial for tetrahedra on main and on this branch.

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