Bug#1043240: transition: pandas 1.5 -> 2.1

[Rebecca N. Palmer]

I'd like to move forward with the pandas 1.5 -> 2.1 transition 
reasonably soon.

Given that pandas 2.x is *not* required for Python 3.12 (but is required 
for Cython 3.0), should we wait for the Python 3.12 transition to be 
done first?

These are broken by pandas 2.x and have a possible (but untested) fix in 
their bug - please test and apply it:
dask(?) dials influxdb-python* python-altair python-feather-format 
python-upsetplot seaborn tqdm*
(* = this package is currently also broken for a non-pandas reason, 
probably Python 3.12, that I don't have a fix for)

These are broken by pandas 2.x and have no known-to-me fix:
augur cnvkit dyda emperor esda mirtop pymatgen pyranges python-anndata 
python-biom-format python-cooler python-nanoget python-skbio python-ulmo 
q2-quality-control q2-demux q2-taxa q2-types q2templates sklearn-pandas
Some generic things to try are pandas.util.testing -> pandas.testing, 
.iteritems() -> .items(), and if one exists, a more recent upstream version.

Is this an acceptable amount of breakage or should we continue to wait? 
Bear in mind that if we wait too long, we may be forced into it by some 
transition further up the stack (e.g. a future Python or numpy) that 
breaks pandas 1.x.

Build logs:
https://launchpad.net/~rebecca-palmer/+archive/ubuntu/pandas2p1/+builds?build_text=&build_state=failed
https://launchpad.net/~rebecca-palmer/+archive/ubuntu/pandas2p1n/+builds?build_text=&build_state=failed
(The second is more recent, but includes fewer packages.)

Autopkgtest logs:
https://qa.debian.org/excuses.php?experimental=1&package=pandas
(Because of the Python 3.12 transition, this may currently be wrong 
about what is a regression and what is not.)