implement CI matrix

this MR implements multiple test scenarios for different python and matplotlib versions

assigned to @philipp.sommer

changed title from Ci matrix to implement CI matrix

merged

added 2 commits

• 5e0702e4 - add test scenarios
• bd88dd23 - do not use pytest-xdist

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marked this merge request as draft

added 1 commit

• 69f74fdc - add pip lock files

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marked this merge request as ready

enabled an automatic merge when the pipeline for 69f74fdc succeeds

mentioned in commit 8aac1bee