(MODULES-10899) Fix for debian10/experimental with tests
This commit introduces the $_module_id variable which will be
populated with the correct module ID based on the version specified.
This makes things a bit more explicit and easier to follow.
Also, two spec tests added for the following scenario:
- Debian 10 (out of the box) using PHP 7.3
- Debian 10 (experimental) using PHP 8.0