WarpX class : current_centering_* variables no longer static #22869

Job	Run time
GCC Minimal w/o MPI	1m 12s
GCC 1D & 2D w/ MPI, QED tools	1m 11s
GCC 3D & RZ w/ MPI, single precision	1m 11s
GCC ABLASTR w/o MPI	46s
Clang pywarpx	1m 11s
	5m 31s

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