[InstCombine] Guard foldICmpSRemConstant against zero divisors (#173702)

instcombine can create srem X, 0 or icmp ult X, 0 mid-pass when
operands fold to zero, which trips assertions in foldICmpSRemConstant.
Bail out on zero divisors / zero ULT constants instead of asserting,
and add a regression test from the minimized reproducer.

This was found by a fuzzer I'm working on.  The high-level design is to
randomly generate LLVM IR, run a pass on it, and then run the original
and new IR through the interpreter.  They should produce the same
results.  Right now I'm only fuzzing instcombine.

GitOrigin-RevId: 5243501cca02d7e54294d4bb5de0a85b06c40b7d