[VectorCombine] Use isSafeToSpeculativelyExecute to guard VP scalarization (#69494)

Previously we were just matching against a fixed list of VP intrinsics
that we
knew couldn't be speculated, but we can reuse the logic in
isSafeToSpeculativelyExecuteWithOpcode. This also allows speculation in
more
cases, e.g. when the divisor is known to be non-zero.

Unfortunately we can't reuse the exact same function call for VP
intrinsics
with functional intrinsics instead of opcodes, because
isSafeToSpeculativelyExecute needs an instruction that already exists.
So this
just copies the logic by peeking into the function attributes of the
intrinsic.