Add clang 16 support and improve compilation time

[rath3t]

• New Cmake flag ENABLE_TEST_COVERAGE_SOURCEBASED to enable the source-based COVERAGE information. The CI still uses the gcov information though
• Huge speed up for Code coverage CI action, from killed by OOM after 50min, we are down to 7min!
• The tests now are run and check additionally with clang-16 and Ikarus fully supports this now.
• Due to the clang support several refactorization took place from recommendations of iwyu and looking at the data generated by ClangBuildAnalyzer

Breaking changes

• Ikarus::ILinearSolver is no template anymore. There is now Ikarus::ILinearSolver, which uses double by default, and which is moved to a source file. Use Ikarus::ILinearSolverT<...>, if you need fancy scalar types.
• The existing materials are now also double by default and are moved to source files, again use e.g. Ikarus::StVenantKirchhoffT<...>, if you need fancy scalar types

These changes reduces the compilation time of the tests significantly. E.g. GCC-Release took 10.5min before and now needs 7.5min GCC-Debug took 21min before and now needs 9min

The variants with clang-16, which are newly introduced: Clang-Debug takes 8min Clang-Release takes 11min

But overall clang seems to be faster, which is therefore the new recommended compiler

[codecov[bot]]

Codecov Report

Merging #186 (bb4db06) into main (af73d33) will increase coverage by 0.26%. Report is 10 commits behind head on main. The diff coverage is 91.20%.

@@            Coverage Diff             @@
##             main     #186      +/-   ##
==========================================
+ Coverage   90.58%   90.85%   +0.26%     
==========================================
  Files          43       42       -1     
  Lines        2040     1870     -170     
  Branches       13        0      -13     
==========================================
- Hits         1848     1699     -149     
+ Misses        182      171      -11     
+ Partials       10        0      -10     

Flag	Coverage Δ
tests	90.85% <91.20%> (+0.26%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
ikarus/assembler/simpleAssemblers.hh	100.00% <100.00%> (ø)
ikarus/assembler/simpleAssemblers.inl	100.00% <100.00%> (ø)
ikarus/finiteElements/feBases/autodiffFE.hh	100.00% <100.00%> (ø)
ikarus/finiteElements/feBases/powerBasisFE.hh	100.00% <ø> (ø)
ikarus/finiteElements/mechanics/linearElastic.hh	89.13% <100.00%> (-9.12%)	:arrow_down:
...teElements/mechanics/materials/linearElasticity.hh	100.00% <100.00%> (ø)
ikarus/io/resultFunction.hh	77.77% <100.00%> (-17.23%)	:arrow_down:
ikarus/linearAlgebra/dirichletValues.hh	100.00% <ø> (ø)
ikarus/solver/linearSolver/linearSolver.hh	100.00% <100.00%> (+77.64%)	:arrow_up:
ikarus/utils/basis.hh	100.00% <ø> (ø)
... and 13 more

... and 19 files with indirect coverage changes

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