Cleanup old settingsgen, zip compression and related env vars and module vars

[mkundu1]

will do after the next version of PyFluent is stabilized in Fluent 25.2

[mkundu1]

Also, review the following code in flobject.py in light of the new settingsgen:

        original_pname = pname
        i = 1
        if parent_taboo:
            while pname in parent_taboo:
                pname = f"{original_pname}_{i}"
                i += 1
        parent_attr_name = pname
        if info.get("file_purpose"):  # not generalizing for performance
            while pname in _bases_by_class and _bases_by_class[pname] != bases:
                pname = f"{original_pname}_{i}"
                i += 1
            _bases_by_class[pname] = bases