Joanne reports that for N79 and DL NR ARFCN 720000 dl2ssb returns that
same 720000 and a phone cannot connect to the base station. In contrast
Amarisoft lteenb chooses SSB NR ARFCN = 720288 for the above setup and
the phone connects ok.

The problem turns out to be that in b8065120 (nrarfcn: New package to do
computations with NR bands, frequencies and NR-ARFCN numbers.) I missed
that the table for Applicable SS raster entries besides GSCN range for
each band also specifies conditions for which particular GSCNs are
allowed to be used inside that range. For example for N79 it is only
GSCNs that are multiple of 16:

https://github.com/blevic/nrarfcn/blob/7ece6a11/nrarfcn/tables/applicable_ss_raster_fr1.py#L60

Besides missing the "multiple of" condition, I also missed exceptional
note conditions where instead of providing a range TS 38.104 specifies
particular set of allowed GSCNs. For example for N39 and SCS=15 kHz only
the following set of GSCNs is allowed to be used for SSB:

    {4707, 4715, 4718, 4729, 4732, 4743, 4747, 4754, 4761, 4768, 4772, 4782, 4786, 4793}

https://github.com/blevic/nrarfcn/blob/7ece6a11/nrarfcn/tables/applicable_ss_raster_fr1.py#L39
https://github.com/blevic/nrarfcn/blob/7ece6a11/nrarfcn/tables/applicable_ss_raster_fr1.py#L13

-> Fix SSB calculation logic to take all that into account. This fixes
N79 case and also highlights previous problems in our tests for
above-mentioned n39 and for "multiple of" and "exceptional" cases in FR2.

Also add explicit test for N77 because we use that band in the ORS.

/reported-by @jhuge
/reported-on nexedi/slapos!1729 (comment 227244)