feat: port NumberTheory.ClassNumber.Finite (#5337)

Co-authored-by: Chris Hughes <chrishughes24@gmail.com>
Co-authored-by: Riccardo Brasca <riccardo.brasca@gmail.com>

Author: 3 people

Mathlib.lean

@@ -2304,6 +2304,7 @@ import Mathlib.NumberTheory.BernoulliPolynomials
 import Mathlib.NumberTheory.ClassNumber.AdmissibleAbs
 import Mathlib.NumberTheory.ClassNumber.AdmissibleAbsoluteValue
 import Mathlib.NumberTheory.ClassNumber.AdmissibleCardPowDegree
+import Mathlib.NumberTheory.ClassNumber.Finite
 import Mathlib.NumberTheory.Cyclotomic.Basic
 import Mathlib.NumberTheory.Cyclotomic.Discriminant
 import Mathlib.NumberTheory.Cyclotomic.PrimitiveRoots