mathlib3

0009ffba - refactor(linear_algebra/charpoly): split file to reduce imports (#13778)

refactor(linear_algebra/charpoly): split file to reduce imports (#13778) While working on representation theory I was annoyed to find that essentially all of field theory was being transitively imported (causing lots of unnecessary recompilation). This improves the situation slightly. Co-authored-by: Scott Morrison <scott.morrison@gmail.com>