[cpp] Update pet buffs to set themselves as initial target for AoEs

[MowFord]

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• 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?

AoE petskills weren't including the pet itself, this PR fixes that. Closes #4996 .

Steps to test these changes

To show that it doesn't target party-member's pets:
https://imgur.com/G5TaRBE

and here's the message showing up properly like retail:

Suspected the primary target message is what made the text color slightly different, confirmed: