SIMD: Align Particle Properties

[ax3l]

For loading/writing SIMD packaged data efficiently, we want to use stdx::vector_aligned

For this to work, we need to properly align the AMReX SoA attributes.

By default, we can use the "native" size (in elements) for this, but in practice I implemented #4520 in a way that also multiples of that size can be used in user-code, to make use of ILP. That said, I have not yet seen big benefits of the latter, but likely because I did not benchmark a lot with small sims that can fit all their particle data into L1/L2/L3.

Follow-up to #4520