David Grote

Thanks for this PR! This will be very useful to have. I have some comments aimed toward improving the code.

@ax3l In general terms, this PR is probably not needed. I only needed this consistency since I'm working on tracking down a problem in the implicit implementation that only occurs...

Is `update_with_rho` needed under the same conditions as Cartesian, i.e. true with Galilean? Would that be affecting the two CI tests?

Could the test for Galilean for Cartesian also be used here? I.e. remove the `# ifndef WARPX_DIM_RZ` so the check is done for all cases.