[REQ] Support quaternion indexing on the rhs of expressions

### Description
Allow users to extract quaternion values by attribute.

### Example
```python
@wp.kernel
def quat_extract_attribute(x: wp.array(dtype=wp.quat), y: wp.array(dtype=float)):
    tid = wp.tid()

    a = x[tid]
    b = a.x + float(2.0) * a.y + 3.0 * a.z + 4.0 * a.w
    y[tid] = b
```