[Magic] Cleanup enfeebling songs

[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?

• Add MACC logic for soul voice/marcato
• Remove unnecesary steps and columns in file.
• Correct effect of gear on potency, macc and such.
• Overall cleanup and simplification.

But I asked copilot, because I was bored, and this is what it had to say:

1. scripts/effects/elegy.lua
   • Optimized the application and removal of the HASTE_MAGIC mod.
2. scripts/effects/threnody.lua
   • Optimized the application and removal of the sub-power effect.
3. scripts/globals/combat/magic_hit_rate.lua
   • Added magicAccuracyFromSoulVoiceMultiplier function.
   • Updated calculateActorMagicAccuracy to include the new multiplier.
4. scripts/globals/magic.lua
   • Removed handleThrenody function as part of cleanup and optimization.
5. scripts/globals/spells/enfeebling_song.lua
   • Significant refactoring and simplification of song-related logic.
   • Consolidated calculations for song power and duration.
   • Removed redundant and complex logic, improving readability and maintainability.
6. scripts/globals/spells/enfeebling_spell.lua
   • Streamlined the nullification check logic.
   • Simplified the main function for enfeebling spells.

Steps to test these changes

Cast songs. Preferably while your party is dying.