Added EntityInitializerLayer specialization for initializing polyhedron subentites 3 -> 2 from cell seeds + other minor mesh refactoring

Refactored mesh initialization to reduce number of calls to SubentitySeedsCreator and number of dynamic allocations

removed redundant subentitiesCounts array from SubentityStorageLayer of dimension 1 for polygonal meshes

Meshes/Geometry: refactored polygon and polyhedron decomposition into templated EntityDecomposer struct with specializations

- added function getPlanarMesh for correcting non-planar polygons in 3D polygon and polyhedral meshes
- added unit tests for getPlanarMesh function
- refactored getDecomposedMesh specialization for polygons by creating PolygonDecomposer struct to reuse decomposing logic in getPlanarMesh function
- other minor refactoring in Meshes/MeshGeometryTest.h

- modified getEntityMeasure specialization for polyhedrons to remove restriction regarding the ordering of vertices, but now it only works for convex polyhedrons
- added function for decomposing polygonal mesh into triangular mesh
- added function for decomposing polyhedral mesh into tetrahedral mesh

- added getEntityMeasure specializations for 2D and 3D polygon, pyramid, wedge, polyhedron
- added unit tests for new getEntityMeasure specializations
- added function isPlanar for checking whether all points of a 3D polygon are on the same plane
- added unit test for function isPlanar
- refactored isDynamicTopology type trait to avoid warning

- added wedge and pyramid topologies
- modified mesh initialization related classes to handle wedge and pyramid topologies
- added entries for wedge and pyramid into VTKTraits, MeshTypeResolver, tnl-mesh-converter
- added unit tests for mesh with two wedges and mesh with two pyramids

- modified VTKReader and VTUReader to handle reading meshes with mixed cell shapes, that can be generalized to polygons
- modified VTKWriter and VTUWriter to handle writing Polygonal meshes

- added Polygon specialization for EntitySeed and EntitySeedHash that uses Array instead of StaticArray to handle variable number of cornerIds
- refactored template argument EntityDimensionTag of SubentitySeedsCreator to EntityTopology to allow specializing for Polygons
- added Polygon specialization for SubentitySeedsCreator to handle variable amounts of vertices per polygon
- added getSubentitiesCount function to SubentitySeedsCreator to retrieve number of subentities to be created from passed in vertices
- modified Initializer::initSubentityMatrix function to retrieve capacities from a method argument instead of creating them statically from traits and to pass in retrieved capacities to Mesh::setSubentitiesCounts
- removed EntityInitializer::initSubvertexMatrix function and replaced all calls to it with Initializer::initSubentityMatrix
- modified EntityInitializerLayer::initSuperentities and InitializerLayer::initEntities functions to calculate subentity matrix capacities before a call to Initializer::initSubentityMatrix

- added SubentityMatrixType to MeshSubentityTraits and modified SubentityMatrixType in MeshTraits to get SubentityMatrixType from MeshSubentityTraits based on Dimension and Subdimension template arguments
- refactored template argument EntityTopologyDimensionTag of SubentityStorageLayer back to EntityTopology to allow specializing for Polygon
- added Polygon specialization for MeshSubentityTraits that uses different SubentityMatrixType and leaves out any count related defined types
- added Polygon specialization for SubentityStorageLayer, that unlike SubentityStorageLayer used in other cell topologies, additionaly stores subentiesCounts
- added setSubentitiesCounts function to mesh and its storage related parent classes for setting subentitiesCounts in SubentityStorageLayer
- modified getSubentitiesCount function in mesh to pass the unused entityIndex parameter to StorageBaseType::getSubentitiesCount to enable retrieving variable subentitiesCounts from Polygon specialization of SubentityStorageLayer

- added Polygon to Topologies
- added mapping of Topologies::Polygon to EntityShape::Polygon in VTKTraits
- added a missing reference to a variable in MeshBuilder::validate

mesh refactoring: moved points from StorageLayerFamily to Mesh, replaced template argument EntityTopology of SubentityStorageLayerFamily and SuperentityStorageLayerFamily by DimensionTag

Move-constructors with a 'const' argument do not make sense. And the
ChunkedEllpack and SlicedEllpack implementations did not even use
std::move!

Documentation for linear solvers and preconditioners

See merge request !116