add python simulator refinement test

[nicolasaunai]

We do not test refinement for E or B.

• Unit tests in tests/amr/data/field/refine only use the Default refinement operator.
• test_field_level_ghosts_via_subcycle_and_coarser_interpolation (currently skipped, see test field level ghosts via subcycles and coarser interpolation #748) does not apply to E or B since they are not time interpolated (anymore).

We need a simulator-based test that checks if electric and magnetic fields are refined as expected.
I think this should be a simulator/initialize kind of test since we do not care about time here, only to check that, given E and B on L0, it is as expected on all patches of L1.

[nicolasaunai]

refine_magnetic and refine_electric functions are not used except in refine_time_interpolate (only used itself in the level ghost field advance test)