More updates for universal polynomials

[lgoettgens]

To get oscar-system/Oscar.jl#3958 going.

I verified locally, that with this branch the GCT.jl tests succeed both with AA 0.41.x (via Oscar 1.1.1) and with AA 0.42.0 (via https://github.com/oscar-system/Oscar.jl/tree/th/buuuump).

It would be great if @fingolfin could merge and release this so that we can proceed with oscar-system/Oscar.jl#3958.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.16%. Comparing base (cd48ab9) to head (bea6a28).

❗ There is a different number of reports uploaded between BASE (cd48ab9) and HEAD (bea6a28). Click for more details.

HEAD has 5 uploads less than BASE

Flag	BASE (cd48ab9)	HEAD (bea6a28)
	6	1

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #87       +/-   ##
===========================================
- Coverage   70.37%   44.16%   -26.22%     
===========================================
  Files          10       10               
  Lines         908      908               
===========================================
- Hits          639      401      -238     
- Misses        269      507      +238     

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