[mlir][vector] Add vector.transpose with unit-dim to vector.shape_cast pattern (#72105)

This patch extends the vector.transpose lowering to replace:

vector.transpose %0, [1, 0] : vector<nx1x<eltty>> to vector<1xnx<eltty>>

with:

  vector.shape_cast %0 : vector<nx1x<eltty>> to vector<1xnx<eltty>>

Source with leading unit-dim (inverse) is also replaced. Unit dim must
be fixed. Non-unit dim can be scalable.

A check is also added to bail out for scalable vectors before unrolling.