Modernize Renovate config

[abrain]

• apply best practices
• group test and linter packages
• remove approval for major versions, but open PRs for each major version separately
• maintain the lockfile on a weekly basis

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 25.71%. Comparing base (03c0a66) to head (53a7c81).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #312   +/-   ##
==========================================
  Coverage      25.71%   25.71%           
  Complexity      1607     1607           
==========================================
  Files             81       81           
  Lines           6214     6214           
==========================================
  Hits            1598     1598           
  Misses          4616     4616           

Flag	Coverage Δ
integration	12.00% <ø> (ø)
unit	15.27% <ø> (ø)

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