cleaning and fixes for PureSoA ParticleTile

[AlexanderSinn]

Summary

• fix return by value/reference mismatch of id() and cpu() with decltype(auto)
• remove dangerous functions data and dataPtr form ArrayOfStructs (they should have returned ParticleType* but returned the position array of the first particle)
• update packParticleData and unpackParticleData for PureSoA
• change getSuperParticle and add setSuperParticle for PureSoA. Remaining issue: super particle has redundant/unused fields for positions, id and cpu
• update ConstParticleTileData for PureSoA
• don’t call getParticleTileData in ParticleTile::id() etc. as this could be very slow if used in a for loop
• use if constexpr instead if SFINAE in a number of places
• change PODVector constructor so that getParticleTileData() won't allocate memory if no runtime components are used

Additional background

Follow-up to #2878.

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate

[ax3l]

Epic changes all along. Thanks a lot! 🚀 ✨

[atmyers]

I agree that these are weird, but unfortunately they are needed for backwards compatibility with codes that still pass particle structs into Fortran subroutines.

[ax3l]

Should we potentially make the void* pointers to reflect what they do?

(Can be a separate PR.)

[ax3l]

Ah I see, changed to ParticleType* is also good.