* Upgrade to new lockfile format

Now requires poetry >= 1.2.2 to read and poetry >= 1.3.0 to write.

Cheat sheet:

```
poetry --version
poetry show > scratch/before
pipx upgrade poetry
poetry --version
poetry show > scratch/after
diff scratch{before,after} && echo "no change!"
```

* Use Poetry 1.3.2 when reading or writing lockfile

* Remove unneeded(?) poetry dep for cibuildwheel

* Update docs

* Remove redundant call to setup-python

* Remove outdated comments related to Poetry 1.x

* Remove outdated docs line

was fixed in #13082

* Minor improvements to poetry cheat sheet

* Invoke setup-python-poetry with explicit version

Not sure about this. It's hardcoding versions everywhere.

* Changelog

* Check the lockfile is version 2.0

Might one day incorporate other checks like #14742

* Typo fixes, thanks Sean

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

Fixes #13655

This change uses ICU (International Components for Unicode) to improve boundary detection in user search.

This change also adds a new dependency on libicu-dev and pkg-config for the Debian packages, which are available in all supported distros.

The --force flag of dpkg-statoverride has been deprecated (apparently starting
with the dpkg version in Debian buster). It offers --force-all as q quick fix,
but the usage in the Debian postinst script is probably covered by
--force-statoverride-add.

Fixes: #8391

Signed-off-by: Jörg Behrmann <behrmann@physik.fu-berlin.de>