CI / test improvements

[jenshnielsen]

increase dependabot limit to 20

There are times where a lot of jobs are opened on the same day
There is no benefit for not opening all of them at once

xfail a test that randomly fails on windows due to time resolution

run min requirements tests with parallel / serial split

These have the same random failures as the regular tests

[codecov]

Codecov Report

Merging #4530 (5266b43) into master (5266b43) will not change coverage.
The diff coverage is n/a.

❗ Current head 5266b43 differs from pull request most recent head 2b28c0f. Consider uploading reports for the commit 2b28c0f to get more accurate results

@@           Coverage Diff           @@
##           master    #4530   +/-   ##
=======================================
  Coverage   68.00%   68.00%           
=======================================
  Files         295      295           
  Lines       31407    31407           
=======================================
  Hits        21358    21358           
  Misses      10049    10049