Add python 3.14 release candidate to advancedtools pipeline

See merge request !130

Enable validation in table_json_conversion.convert.to_dict for use in XLSX-converter

See merge request !129

See merge request !128

Remove support for Python 3.8

See merge request !127

Fix pylint errors

See merge request !126

XLSXConverter paths validation

See merge request !125

- In export_related.py export() we do not care which Exception is raised & need to continue
- In import_from_xml.py import_xml() the File from which the _checksum is deleted is created within this method
- In table_export.py BaseTableExporter.collect_information(), the method called by _call_find_function is not set, so determining which exceptions may be raised is difficult
- table_importer.py TSVImporter.read_file() only exists for backward compatibility