Particles Container: Polymorphic Arena & Runtime

[ax3l]

As discussed, in order to simplify Python variants and code coupling, we want to make two changes to the HiPACE++ particle containers:

• use the PolymorphicArena to have the CPU/GPU/pinned allocation decided at runtime (as we do for MultiFabs)
• make every component (including/excluding positions, but ideally including them) a runtime attribute

X-ref: same efforts in WarpX (BLAST-WarpX/warpx#5779) and ImpactX (BLAST-ImpactX/impactx#901).