[mlir][VectorOps] Add deinterleave operation to vector dialect

The deinterleave operation constructs two vectors from a single input
vector. Each new vector is the collection of even and odd elements
from the input, respectively. This is essentially the inverse of an
interleave operation.

Each output's size is half of the input vector's trailing dimension
for the n-D case and only dimension for 1-D cases. It is not possible
to conduct the operation on 0-D inputs or vectors where the size of
the (trailing) dimension is 1.

The operation supports scalable vectors.

Example:
```mlir
%0 = vector.deinterleave %a
           : vector<[4]xi32> -> vector<[2]xi32>
%1 = vector.deinterleave %b
           : vector<8xi8> -> vector<4xi8>
%2 = vector.deinterleave %c
           : vector<2x8xf32> -> vector<2x4xf32>
%3 = vector.deinterleave %d
           : vector<2x4x[6]xf64> -> vector<2x4x[3]xf64>
```

Author: mub-at-arm