deprecate constructing number-field fractional ideals via orders' .ideal() method

[yyyyx4]

Fixes #34806.

[codecov-commenter]

Codecov Report

Base: 88.57% // Head: 88.58% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (795e463) compared to base (52a81cb).
Patch coverage: 95.23% of modified lines in pull request are covered.

❗ Current head 795e463 differs from pull request most recent head 71361e7. Consider uploading reports for the commit 71361e7 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #34979      +/-   ##
===========================================
+ Coverage    88.57%   88.58%   +0.01%     
===========================================
  Files         2140     2136       -4     
  Lines       397273   396154    -1119     
===========================================
- Hits        351891   350945     -946     
+ Misses       45382    45209     -173     

Impacted Files	Coverage Δ
src/sage/modular/dirichlet.py	94.03% <ø> (ø)
src/sage/rings/padics/padic_valuation.py	92.48% <ø> (ø)
src/sage/rings/quotient_ring.py	88.40% <90.90%> (+0.01%)	⬆️
src/sage/rings/number_field/bdd_height.py	99.18% <100.00%> (-0.01%)	⬇️
src/sage/rings/number_field/number_field.py	93.59% <100.00%> (ø)
src/sage/rings/number_field/order.py	92.85% <100.00%> (+0.03%)	⬆️
...c/sage/schemes/elliptic_curves/ell_number_field.py	92.26% <100.00%> (+0.01%)	⬆️
src/sage/schemes/elliptic_curves/heegner.py	90.91% <100.00%> (ø)
src/sage/schemes/projective/projective_point.py	91.02% <100.00%> (+0.07%)	⬆️
...e/combinat/cluster_algebra_quiver/mutation_type.py	49.64% <0.00%> (-2.50%)	⬇️
... and 102 more

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[pjbruin]

According to the logs there was one failing doctest, in schemes/elliptic_curves/ell_field.py; I checked locally that tests pass, so this was probably just a random failure.

[github-actions]

Documentation preview for this PR is ready! 🎉
Built with commit: 71361e7

[yyyyx4]

Thank you!