Add TBC Support

[NoM0Re]

Description

Fixes #6096

This PR adds The Burning Crusade (TBC) support and includes several refactors and fixes required to make WeakAuras function correctly on TBC realms.
Overall, TBC support appears stable on PTR and no major issues are expected, but the points listed below in the Maintainer Notes are worth being aware of.

Type of change

• New Expansion

How Has This Been Tested

• Tested on TBC PTR
• Verified most aura loading, triggering, ...

Details / Notes

• Wrath Mini Widget is reused in both Load and Trigger for TBC
• Init refactor to make the structure clearer (still large, but more maintainable)
• Small refactor under Private.event_prototypes for expansion checks
• AddMessageEventFilter now works correctly on TBC
• Private.power_types cleanup and table refactor
• Proc Glow exists on TBC 🎉
• Models regenerated, but it is already a few builds old
• Arthas is currently missing; temporarily replaced with Illidan

Maintainer Notes / Open Points

This PR includes TBC support and works correctly on PTR in its current state. That said, there are a few open points worth calling out explicitly:

TalentWidget edge cases

• Importing a class that does not exist on TBC (e.g. Death Knight) currently causes errors.
  This can be purged and does not block TBC support.
  A fix has been added here:
  https://github.com/WeakAuras/WeakAuras2/compare/eaf439b50fad4bbf8aa58ee72b33573a3a1fa8f6..67a3f2617ce1e7a93d1315482fd6d26b56a5fa78

• More critically: when switching talent widgets while a talent index is selected that no longer exists (due to class change or import), the widget will still attempt to validate that index.
  As a result, the aura may fail to load or trigger.

  • A temporary fix has been added here:
    https://github.com/WeakAuras/WeakAuras2/compare/eaf439b50fad4bbf8aa58ee72b33573a3a1fa8f6..67a3f2617ce1e7a93d1315482fd6d26b56a5fa78
  • This fix is intentionally a band-aid.
  • A proper solution would be a validator that runs after every import and input change to ensure referenced talents actually exist.

Modernizer & merge order

• The currently committed Modernizer should also apply to TBC.
• Because of this, it would be cleaner to merge TBC before tagging, although this is not a hard requirement.

Pet Power: Happiness

• Currently not supported at all.
• Should be implemented as a proper power type.
• Missing not only for TBC, but also for Classic and Wrath.

Model

• Arthas model is missing and temporarily replaced with Illidan.
• Feedback welcome on whether this is acceptable or should be reverted.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings