MAINT: Refactored helper functions.

src/caosadvancedtools/table_json_conversion/fill_xlsx.py

...aosadvancedtools/table_json_conversion/table_generator.py

src/caosadvancedtools/table_json_conversion/utils.py

src/caosadvancedtools/table_json_conversion/xlsx_utils.py

unittests/table_json_conversion/test_fill_xlsx.py

...ts/table_json_conversion/test_table_template_generator.py