Move schema of peer cells into under peer/cell/lte and peer/cell/nr with
keeping in mind that peer/cell will become a separate entity in MultiRU.

NR deduplication is straightforward, but for LTE original ncell_list used
`cell_id` name for full E-UTRAN cell identity. peer/cell/lte uses e_cell_id
name for that and content of that peer/cell/lte cannot be applied directly to
ORS's ncell_list and ncell_list in current enb/generic. To keep things working
we pickup peer/cell/lte field by field with mapping e_cell_id into cell_id. For
the reference for NR both original ncell_list and new peer/cell/nr use
nr_cell_id for full 5G cell identity.

Backward compatibility: nothing practically changes for ORS and generic.