installation: moved from `setup.py` to `pyproject.toml`: - updated installation to use the now standard `pyproject.toml` instead of legacy `setup.py`. `setup.py` and other legacy files have been deleted. - removed outdated README4PACKAGERS - removed pylintrc which has not been correctly reviewed. Linter conf should go to `pyproject.toml` now. - [hatch](https://hatch.pypa.io) is now used as main building tool. However, thanks to the use of standards, other tools can be used too. - update .hgignore - several dependencies version bump, with code update to adapt to changes.

You'll find install instructions in documentation (see doc/installation.rst).

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