[CostModel] Align the cost model for intrinsics for scalable/fixed-width vectors.

Let getIntrinsicInstrCost call getTypeBasedIntrinsicInstrCost for scalable vectors,
similar to how this is done for fixed-width vectors, instead of falling back
on BaseT::getIntrinsicInstrCost().

If the intrinsic cannot be costed (or is not overloaded by the target),
it will return InstructionCost::getInvalid() instead.

Depends on D97469

Reviewed By: david-arm

Differential Revision: https://reviews.llvm.org/D97470