[SDag] Fold saddo[_carry] with bitwise-not argument to ssubo[_carry] (#66571)

Fold `(saddo (not a), 1)` to `(ssubo 0, a)` and
`(saddo_carry (not a), b, c)` to `(ssubo_carry b, a, !c)`.

Proof: https://alive2.llvm.org/ce/z/Lj49YM

This is the same as https://reviews.llvm.org/D46505 and
https://reviews.llvm.org/D59208, but for signed opcodes.