- adapted the get_band function: the algorithm is now taking into account
  also the UL frequency in order to fetch the proper band (this was failing
  before as some NR bands have the same DL band, e.g. band 65 and 66)
- added new bands to the NR table as per TS 38.101 V16.4.0 (2020)
- made the from_nrarfcn function compatible with UL FDD (this function,
  used for both DL and UL  was previously working with TDD only as it
  did not compute properly the frequency for the UL FDD, throwing asserts)
- introduced common functions to get the NR table idx and the duplex mode,
  removing repeated code in the process
- removed the unused function to get the uldl offset
- improved some logging
- other minor fixes to the relevant code