This is almost all find-and-replace.

I manually edited:
* pkgs/development/python-modules/notifications-android-tv/default.nix,
* pkgs/servers/home-assistant/default.nix,
* pkgs/development/tools/continuous-integration/buildbot/master.nix

A few files have not been changed in this PR because they would cause rebuilds.

This PR should have 0 rebuilds.

There is no need to disable Python packages for Python versions that are
no longer in Nixpkgs.
This change was generated using the following script:

    pattern='^\s*disabled\s*=\s*pythonOlder\s*"3\.\([0-9]\|10\)"\s*;\s*$'
    for f in $(find -name '*.nix'); do
        grep -q "$pattern" "$f" || continue
        sed -i "/$pattern/d" "$f"
        if [ $(grep -c pythonOlder "$f") == 1 ]; then
            sed -i '/^\s*pythonOlder,\s*$/d' "$f"
        fi
        nixfmt "$f"
    done

This commit was created by a combination of scripts and tools:
- an ast-grep script to prefix things in meta with `lib.`,
- a modified nixf-diagnose / nixf combination to remove unused `with
lib;`, and
- regular nixfmt.

Co-authored-by: Wolfgang Walther <walther@technowledgy.de>

The “canonical” name of the Python libfdt package, i.e. the one used on
PyPI and, hence, the one that is listed in the requirements of the
dependent modules is `pylibfdt`, but the upstream build system produced
a package called `libfdt`.

Given that, realistically, everyone will be using `pylibfdt`, as seen on
PyPI, our choices are to either patch / jailbreak the requirement in all
dependent packages, or follow PyPI and rename the package itself.

Rename the package once and for all, since it is easier than modifying
every single dependent one.