gh-38346: Updated `__repr__()` to `_repr_()` in ideals classes
    
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This PR aims at updating `__repr__()` method to `_repr_()`, in order to
enable renaming and ensure consistency across various SageMath classes.
@tscrim

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preview.

### ⌛ Dependencies

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URL: #38346
Reported by: 25shriya
Reviewer(s): Travis Scrimshaw

Author: Release Manager

src/sage/rings/ideal.py

@@ -320,7 +320,7 @@ def _repr_short(self):
             return '\n(\n  %s\n)\n' % (',\n\n  '.join(L))
         return '(%s)' % (', '.join(L))
 
-    def __repr__(self):
+    def _repr_(self):
         """
         Return a string representation of ``self``.
 
@@ -1270,7 +1270,7 @@ class Ideal_principal(Ideal_generic):
     #def __init__(self, ring, gen):
     #    Ideal_generic.__init__(self, ring, [gen])
 
-    def __repr__(self):
+    def _repr_(self):
         """
         Return a string representation of ``self``.
 
@@ -1700,7 +1700,7 @@ class Ideal_fractional(Ideal_generic):
 
     See :func:`Ideal()`.
     """
-    def __repr__(self):
+    def _repr_(self):
         """
         Return a string representation of ``self``.
 

src/sage/rings/number_field/number_field_ideal.py

@@ -427,7 +427,7 @@ def __elements_from_hnf(self, hnf):
         K = self.number_field()
         return [K(x, check=False) for x in K.pari_zk() * hnf]
 
-    def __repr__(self):
+    def _repr_(self):
         """
         Return the string representation of this number field ideal.
 
@@ -1862,7 +1862,7 @@ def __init__(self, field, gens, coerce=True):
         else:
             raise ValueError("gens must have a nonzero element (zero ideal is not a fractional ideal)")
 
-    def __repr__(self):
+    def _repr_(self):
         """
         Return the string representation of this number field fractional ideal.