Type stability of functions from examples tree_1d_dgsem

[huiyuxie]

Like #2122 - fix type instability of self-defined functions from examples.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.36%. Comparing base (9fa4e27) to head (e82cf3e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2133   +/-   ##
=======================================
  Coverage   96.36%   96.36%           
=======================================
  Files         480      480           
  Lines       38042    38067   +25     
=======================================
+ Hits        36657    36682   +25     
  Misses       1385     1385           

Flag	Coverage Δ
unittests	96.36% <100.00%> (+<0.01%)	⬆️

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[huiyuxie]

Please review carefully @ranocha

[huiyuxie]

I'm worried about cases like exp(Int) and log(Int) causing Float64 outputs.

[ranocha]

Thanks a lot

[huiyuxie]

Sorry I forgot the type stability for the whole function - thanks for the review 😊

[ranocha]

Thanks