Backports for 1.1.1

[benlorenz]

• catch a corner case for elliptic surfaces #3880
• speedup elliptic surfaces #3884

[HechtiDerLachs]

Notebook on elliptic fibrations is up and running on this branch. Thanks for compiling this!

[codecov]

Codecov Report

Attention: Patch coverage is 88.31169% with 9 lines in your changes missing coverage. Please review.

Project coverage is 83.78%. Comparing base (d0b75de) to head (f0b6eb7).

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.1    #3910      +/-   ##
===============================================
+ Coverage        81.95%   83.78%   +1.82%     
===============================================
  Files              581      581              
  Lines            80160    80220      +60     
===============================================
+ Hits             65697    67211    +1514     
+ Misses           14463    13009    -1454     

Files	Coverage Δ
experimental/Schemes/src/IdealSheaves.jl	78.55% <100.00%> (+6.22%)	⬆️
experimental/Schemes/src/elliptic_surface.jl	87.30% <83.92%> (+82.83%)	⬆️

... and 18 files with indirect coverage changes

[joschmitt]

All notebooks run through without error on this branch (c375d48) and there seem to be no unexpected differences in output (to me as a non-expert). I did not check for any performance regression.

[fingolfin]

Thank you @benlorenz your efforts are much appreciated!