[llvm] [ADT] Add implementations for mulhs and mulhu to APInt (PR #84609)

[Simon Pilgrim via llvm-commits]

================
@@ -3067,6 +3067,22 @@ void llvm::StoreIntToMemory(const APInt &IntVal, uint8_t *Dst,
   }
 }
 
+APInt APIntOps::mulhu(const APInt &C1, const APInt &C2) {
----------------
RKSimon wrote:

add same-bitwidth assertion: `assert(C1.BitWidth == C2.BitWidth && "Bit widths must be the same");`

https://github.com/llvm/llvm-project/pull/84609