mathlib3

2651125b - feat(algebra & polynomial): some (q)smul lemmas+generalisations (#18852)

feat(algebra & polynomial): some (q)smul lemmas+generalisations (#18852) There is many generalisations around these areas too, but I am specifically not doing them as it will be easier done after the port. I am only doing what I need for merging in the splitting field diamond fix. Co-authored-by: Eric Rodriguez <37984851+ericrbg@users.noreply.github.com>