Simplify attribute handling using new @attr features

[lgoettgens]

See Nemocas/AbstractAlgebra.jl#1958 for the changes to @attr. This PR needs to wait for Nemocas/AbstractAlgebra.jl#1958 to get released (x-ref Nemocas/AbstractAlgebra.jl#1963).

Furthermore, this includes #4475. Depending on the result there, this PR may need to get adapted.

This is a draft, since I want to look through all uses of other attribute-related functions like get_attribute and set_attribute! as well and do analogous changes for these as well.

The diff view may be a bit overwhelming and doesn't make much sense for this kind of change; instead you could look at the diff view with whitespace changes ignored: https://github.com/oscar-system/Oscar.jl/pull/4476/files?w=1

pinging some people that may benefit from this PR: @HereAround @simonbrandhorst @HechtiDerLachs

[HechtiDerLachs]

Looks reasonable to me. Let's see how the tests go, when they run. Thanks!

[fingolfin]

Looks good to me but yeah would be good if people whose code this is (@HereAround @HechtiDerLachs @simonbrandhorst) had a look.

[simonbrandhorst]

If the tests pass they pass. I do not see anything suspicious.

[lgoettgens]

Let me re-draft this for the time being. I would prefer to first change the definition of @attr again and adapt this instead of merging this PR and doing a follow-up.

[lgoettgens]

This is now rebased and uses Nemocas/AbstractAlgebra.jl#1966. So we need to wait until that is released in AA.

[codecov]

Codecov Report

Attention: Patch coverage is 85.07937% with 47 lines in your changes missing coverage. Please review.

Project coverage is 84.55%. Comparing base (3932f48) to head (b346152).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Rings/mpoly-localizations.jl	35.29%	11 Missing ⚠️
...ry/Schemes/ProjectiveSchemes/Objects/Attributes.jl	53.84%	6 Missing ⚠️
...ry/Schemes/ProjectiveSchemes/Objects/Properties.jl	75.00%	6 Missing ⚠️
.../AlgebraicGeometry/Schemes/Sheaves/IdealSheaves.jl	87.17%	5 Missing ⚠️
...raicGeometry/Surfaces/EllipticSurface/Morphisms.jl	0.00%	4 Missing ⚠️
...perimental/Schemes/src/ToricDivisors/attributes.jl	80.00%	3 Missing ⚠️
...try/ToricVarieties/cohomCalg/special_attributes.jl	88.23%	2 Missing ⚠️
src/Groups/matrices/form_group.jl	88.88%	2 Missing ⚠️
src/Modules/Posur.jl	77.77%	2 Missing ⚠️
src/Rings/mpoly-ideals.jl	94.59%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4476      +/-   ##
==========================================
- Coverage   84.55%   84.55%   -0.01%     
==========================================
  Files         672      672              
  Lines       88876    88811      -65     
==========================================
- Hits        75145    75090      -55     
+ Misses      13731    13721      -10     

Files with missing lines	Coverage Δ
...heoryTools/src/AbstractFTheoryModels/attributes.jl	100.00% <100.00%> (ø)
...Tools/src/FamilyOfG4Fluxes/special_constructors.jl	77.41% <100.00%> (+0.30%)	⬆️
...ometry/Schemes/AffineSchemes/Objects/Attributes.jl	91.66% <100.00%> (-0.06%)	⬇️
...metry/Schemes/CoveredSchemes/Objects/Attributes.jl	98.18% <100.00%> (-0.04%)	⬇️
...icGeometry/Schemes/FunctionField/FunctionFields.jl	81.10% <100.00%> (-0.08%)	⬇️
...ometry/Surfaces/EllipticSurface/EllipticSurface.jl	83.62% <100.00%> (-0.03%)	⬇️
.../ToricVarieties/NormalToricVarieties/attributes.jl	98.67% <100.00%> (-0.01%)	⬇️
src/Groups/group_characters.jl	96.39% <100.00%> (ø)
src/Modules/mpolyquo-localizations.jl	88.76% <100.00%> (-0.13%)	⬇️
src/Rings/MPolyMap/AffineAlgebras.jl	95.95% <100.00%> (-0.05%)	⬇️
... and 18 more

... and 2 files with indirect coverage changes

[HereAround]

Thank you for working on this @lgoettgens . I am very happy with those changes! Thus, as long as I am concerned, good to be merged.

[HereAround]

@lgoettgens , am I right to assume that you wish to hear from @simonbrandhorst , @HechtiDerLachs and @fingolfin before this PR is being merged? Anything else holding this PR back?

[lgoettgens]

2 approvals are enough for me right now. In case of any issues, we can adjust it again later. But now, let's get it merged, before we get any more conflicts