shuffle abstract method

Shuffle the lane values based on the mask.

The mask must be one of the 256 shuffle masks from xxxx to wwww.

Creates a new Float32x4 whose lane values are taken from the lanes of this value based on the lanes of the shuffle mask, with the result's x lane being taken from the lane of the first letter of the shuffle mask's name, the y lane from the second letter, z lane from the third letter and w lane from the fourth letter.

For example, the shuffle mask wxyz creates a new Float32x4 whose x lane is the w lane of this value, because the first letter of the shuffle mask's name, wxyz is "w". Then the y, z and w lanes of the result are the values of the x, y and z lanes of this value.

The xyzw "identity shuffle" mask gives a result with the same lanes as the original.

Some masks preserve the values of all lanes, but may permute them. Other masks duplicates some lanes and discards the values of others.

For example, doing v1.shuffle(yyyy) is equivalent to Float32x4.splat(v1.y).