Grid: add cells_connectivity and cells_definition

This PR adds two missing Grid properties:

• cells_connectivity: connectivity array as used by ESMF and VTK
• cells_definition: cell definition as used by PyVista and legacy VTK
• cells_offset: location of the start of each cell in cells_connectivity

I also added convenience functions and constants to grid_tools:

• get_cells_matrix: convert cells_connectivity or cells_definition back to the default cells matrix used in the Grid class (can be used to convert VTK-grids into FINAM-grids)
• INV_VTK_TYPE_MAP: Inverse mapping to VTK_TYPE_MAP: FINAM cell type to VTK cell type
• VTK_CELL_DIM: parametric dimension for each VTK cell type

changed milestone to %v1.0

assigned to @muellese

requested review from @mlange

added data design labels

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• 6d27bfc7 - Grid: add cells_offset

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• 71065b10 - grid_tools: add get_cells_matrix

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• aeb958d9 - grid: offsets should start with 0 and end with length of connectivity array
• 5414ade8 - tests: add tests for cells definitions

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marked the checklist item add tests as completed

marked this merge request as ready

approved this merge request

@muellese Don't forget to update the changlog! 😉

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• 2eae07e5 - grid_tools: add INV_VTK_TYPE_MAP and VTK_CELL_DIM maps for VTK conversion

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• 4b1e55a2 - fix isort

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• b073f2ab - update changelog

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• b073f2ab...51cfb36b - 2 commits from branch main
• 08cdfec4 - Merge branch 'main' into 'add_grid_cells_connectivity'

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approved this merge request

mentioned in commit a4b765ba