[lua] Aftermath effect cleanup

[MowFord]

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?

Closes #5231 .

Changes aftermath to encode the aftermath effect the same way on a pet:

• ensure we always give the effect to the pet with the same power/subpower/tier/duration

This then allows us to simplify the onEffectGain/onEffectLose functions to just stack mods on the effect

Steps to test these changes

see that pet gets the mods just like before

and also that aftermath functions the same for player as well:

and just to be sure here's spharai:

and of course there are no errors in map server console