GlobalISel: Try to combine G_[SU]DIV and G_[SU]REM

It is good to have a combined `divrem` instruction when the
`div` and `rem` are computed from identical input operands.
Some targets can lower them through a single expansion that
computes both division and remainder. It effectively reduces
the number of instructions than individually expanding them.

Reviewed By: arsenm, paquette

Differential Revision: https://reviews.llvm.org/D96013