mark scalartype determining functions as non-differentiable

[lkdvos]

Closes #139

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.44%. Comparing base (b93dde0) to head (c7cb61b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #140   +/-   ##
=======================================
  Coverage   88.44%   88.44%           
=======================================
  Files          36       36           
  Lines        3948     3948           
=======================================
  Hits         3492     3492           
  Misses        456      456           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Jutho]

Thanks. Clearly there is no JET in the KrylovKit CI 😄 . Maybe something to add, once it is functional again.