Improve coverage of core library functions

[tcompa]

See https://htmlpreview.github.io/?https://github.com/fractal-analytics-platform/fractal-tasks-core/blob/python-coverage-comment-action-data/htmlcov/index.html

One that obviously requires some extra care is fractal_tasks_core/lib_masked_loading.py

[tcompa]

Refs:

• Update anndata (version and import source of write_elem) #427
• Drop torch dependency fractal-faim-ipa#1

[tcompa]

This is now better as of #459. but there is still room for further improvements.

[tcompa]

As of #459, #467 and #468, the core-library coverage increased significantly:

Module	statements	missing	excluded	branches	partial	coverage
lib_channels.py	106	1	0	58	1	99%
lib_glob.py	19	0	0	8	0	100%
lib_input_models.py	56	0	0	12	0	100%
lib_masked_loading.py	61	9	0	16	6	81%
lib_metadata_parsing.py	98	7	0	30	8	88%
lib_parse_filename_metadata.py	33	1	0	12	1	96%
lib_pyramid_creation.py	27	0	0	10	0	100%
lib_read_fractal_metadata.py	34	0	0	14	0	100%
lib_regions_of_interest.py	135	3	0	42	3	97%
lib_ROI_overlaps.py	158	5	0	62	6	95%
lib_upscale_array.py	73	7	0	48	6	88%
lib_zattrs_utils.py	49	2	0	28	2	95%

Closing for now.