[c++] [Combat] Split enspell damage bonus from weapons

[overefined]

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• 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?

Separates the enspell damage bonus gained from weapons and other items. Weapon enspell damage bonus now only applies to hits from the weapon that gives the bonus.

https://drive.google.com/file/d/1OSThzxK0cGA8IXy_DeQToUu7_KKscKlt/view?usp=sharing

Closes: #4815

Steps to test these changes

1. change class to RDM/NIN
2. !additem 16605
3. !additem 17697
4. cast enspell and attack something