Check for potentially unused test data files and check file sizes only for changed files

[bernt-matthias]

Raise linter error-level to warn. This will require galaxyproject/planemo-ci-action#23 and a new release of the action.

The check for unused test data is clearly not fool proof, e.g. index files. But maybe it helps.

The change in the file size job is to check only changed files. Seems to work, since find tools/anndata -type f -size +500k would return

tools/anndata/test-data/tl.diffmap.h5ad
tools/anndata/test-data/tl.draw_graph.h5ad
tools/anndata/test-data/tl.umap.h5ad
tools/anndata/test-data/pp.neighbors_umap_euclidean.recipe_weinreb17.paul15_subsample.h5ad
tools/anndata/test-data/tl.paga.neighbors_gauss_braycurtis.recipe_weinreb17.paul15_subsample.h5ad

But since none of these files was changed they are not reported.

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