This patch contains two parts.
1. Update costs reflect to the codegen changes. This is not that
accurate since the step vector can use smaller type if there is a
vscale_range attribute. But we cannot get that in the type-based query
in TTI.
2. Return invalid cost for the vector.extract.last.active that needs
vector split for the step vector. But currently this is not handled
correctly and will hit the assertion.
For not blocking the FindLast reduction in LV
(https://github.com/llvm/llvm-project/pull/184931). We should land this
first and fix the SelectionDAG for vector.extract.last.active lowering.
81691d23cd