The new Low ICD format is quite different from Mid's: it contains more
items, and most of them are only sent during the start-of-stream heap,
with data heaps only carrying the time and correlator output data. There
are also items that don't exist anymore because they don't make sense in
Low, plus a new way to encode time in each correlator dump. Overall,
implementing this new ICD marks a clear break from the ICD symmetry we
had until now between Low and Mid.

This commit adds a new user-facing "transmission.telescope" option that
controls the telescope's ICD to follow when generating data for a SPEAD
stream. When using Mid, and since Mid's ICD hasn't changed, the existing
emulation is used, with the exception that now we send CCI data as part
of the correlator output data item (we hadn't done this properly until
now, but never cared about it because the receiver doesn't use this
data). When using Low the new behavior is triggered, with most of the
new Items' values sent in the start-of-stream heaps. Since in
receive-core both ICDs follow a common interface, some of the
differences in the code at this level can be handled without the need of
further if/else branches, which simplifies the code somewhat. A new unit
test also checks that sending both Mid and Low data is successful in a
small 1-data-heap run, and that the receiver gets the items it's
supposed to get with each heap type.

In order to be able to use the new ICD definitions we have upgraded our
dependency on receive-ore to >= 4.0.0. This new version brings breaking
changes, not only in how the ICDs and their items are defined, but also
in that it has a clearer separation between the utility code dealing
with Measurement Set I/O and the ICD, so we have adjusted our usage of
those APIs as well. The new version of receive-core also requires Python
>= 3.10 so we need to upgrade our own Python version dependency
constraints.

A particularity about the Low ICD is that it assumes a single channel
per SPEAD stream, and therefore doesn't send any item indicating the
number of channels. Our emulator follows suit, assuming 1 channel per
stream by default when using the Low telescope, can this behavior can
still be overridden by the user. If they do, then a warning is issued
noting the non-standard behavior being triggered, but still no Item is
sent indicating this; instead the receiver can only infer this
information by inspecting the correlator data output shape to deduce the
number of channels sent.

Although this implementation already follows the new ICD, there are some
details that have been left out of this first iteration, namely:

 * The heap counter doesn't encode any information, partly because the
   python bindings for spead2 don't allow to set the heap counter.
 * Some of the data sent on the start-of-stream heap is hardcoded to
   dummy values instead of using proper ones. This requires some further
   plumbing (new user options, read more data from the input Measurement
   Set), and since at the moment the data is simply logged on the
   receiver there is no rush to get it right yet.
 * There is no re-sending of start-of-stream heaps.

This work is part of YAN-1273.