We turn the algebra of mixed differential forms into a de Rham complex and add it to the category of ChainComplexes, see #31669.

Furthermore, we add de Rham cohomology to SageManifolds with limited functionality. For now, the implementation will only consist of abstract elements that are given by representatives of mixed forms, i.e. we take closed mixed forms, put a bracket around it and do all computations in the algebra of mixed forms.

CC: @egourgoulhon @tscrim @mkoeppe @jhpalmieri

Component: manifolds

Keywords: chain_complex

Author: Michael Jung

Branch/Commit: 566176a

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/31691