Adapt to conformance test changes in AA

[lgoettgens]

Make use of the new submodule structure and names introduced in Nemocas/AbstractAlgebra.jl#1954.

Currently also includes #2035 to prevent conflicts. I'll rebase once that is merged. This also removes a hack that forces some jobs to be executed by the same test worker (cf #2035 (comment)).

[aaruni96]

Looks sensible to me, and parallel tests work on my workstation.

[codecov]

Codecov Report

Attention: Patch coverage is 78.26087% with 5 lines in your changes missing coverage. Please review.

Project coverage is 88.24%. Comparing base (ffd6e31) to head (044e5fb).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/flint/padic.jl	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2036      +/-   ##
==========================================
+ Coverage   88.23%   88.24%   +0.01%     
==========================================
  Files         100      100              
  Lines       36717    36740      +23     
==========================================
+ Hits        32397    32421      +24     
+ Misses       4320     4319       -1     

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