Merge branch 'fix/hybrid-depr-warn' into 'master'

Fix Dune::Hybrid deprecation warnings

Closes #872 (closed)

See merge request !2054 (merged)

(cherry picked from commit 08fbf362)

91009518 [multidomain][fvassembler] Fix Dune::Hybrid deprecation warnings 48ad9e5c [linear][matrixconverter] Fix Dune::Hybrid deprecation warning d296a126 [matrixconverter] Improve readability by using capture default cefe45cd [matrixconverter] Remove unused includes

changed milestone to %3.2

added Backport label

Looks good. I built the multidomain tests with clang and dune 2.6, 2.7 and master. No compiler warnings related to this MR.
Tests pass.

mentioned in commit 16c09483

merged