Unify pyansys_advanced/tox_*.ini files

[jorgepiloto]

🐞 Problem

The tox_*.ini files in pyansys_advanced/{{cookiecutter.__project_name_slug}} are not so different from each other. They just differ in a couple of lines between them.

💡 Solution

Instead of having three of these files, we can benefit from Jinja syntax to have a single file which renders according to the type of build system tool.