[Promyvion] Add elemental functionality to Empty-type mobs

[Xaver-DaRed]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Makes mobs choose an element and change their resistances, model and subanimation accordingly.
Loot variation depending on element chosen will be handled in a different PR.

Also adds a testing module that compares a lot of different empty models and subanimations. Its meant for testing purposes, for the inevitable time this has to be revisited.

Steps to test these changes

Run promyvions. Yeah, it still is boring without level cap, but mobs have random elements now.