Add overload for getParticleCell that returns local cell index

[roelof-groenewald]

Summary

In WarpX we have a few routines that requires the local cell index of particles (i.e. the cell number in the current box). The AMReX function getParticleCell currently only has logic to return the global cell index (relative to the domain low end). This PR adds a new overload for that function which does not shift the cell index based on the global box index.

Additional background

See ECP-WarpX/WarpX#5118 for WarpX context.

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

[atmyers]

Hi @roelof-groenewald - thanks for this! Could you add short docstrings to these functions that explain the difference between them?