GRHD: fix atmosphere freezing and evolution logic (!199)

Fixes the following issues with the current implementation:
- `update_atm_domain_of_dependence!` did not distinguish between points
  1. whose neighbors are also in the bulk,
  2. where one neighbor is on an interface,
  3. where the point itself is on an interface.

  These cases are already properly handled in 2d.
- `stop_atmosphere_evolution_*` methods did not account for the `c2p_freeze_atm` flag, which essentially prevented the atmosphere to ever evolve.
- `update_atm_domain_of_dependence!` was activated by setting `c2p_dynamical_atm`, but it should be controlled by `c2p_enforce_causal_atm`



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Additional fixes with less impact:
- remove unused parameter `id_atmosphere_density` from `GRHD` section
- `c2p_set_atmosphere_on_failure` should really suppress any errors appearing in the cons2prim