mathlib3

0bfc68fc - feat(ring_theory/witt_vector/structure_polynomial): witt_structure_int_prop (#4466)

feat(ring_theory/witt_vector/structure_polynomial): witt_structure_int_prop (#4466) This is the 3rd PR in a series on a fundamental theorem about Witt polynomials. Co-Authored-By: Rob Y. Lewis <rob.y.lewis@gmail.com>