Add downgrade CI

[MartinuzziFrancesco]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Ref. SciML/SciMLBase.jl#553

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8098a2d) 86.47% compared to head (90c23a2) 86.47%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #185   +/-   ##
=======================================
  Coverage   86.47%   86.47%           
=======================================
  Files          12       12           
  Lines         599      599           
=======================================
  Hits          518      518           
  Misses         81       81           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.