Remove channel_id from GeometryID

This MR reallocates the bits to the other id components. The distribution is now:

constexpr static geo_id_value volume_mask    = 0xff00000000000000; // 255 volumes
constexpr static geo_id_value boundary_mask  = 0x00ff000000000000; // 255 boundaries
constexpr static geo_id_value layer_mask     = 0x0000fff000000000; // 4095 layers
constexpr static geo_id_value approach_mask  = 0x0000000ff0000000; // 255 approach surfaces
constexpr static geo_id_value sensitive_mask = 0x000000000fffffff; // (2^28)-1 sensitive surfaces

Closes #572 (closed)