Plague Rebuild Redux

[edmund-h]

credit to @ElMariuso and @helloruhe for work on the original plague rework. unfortunatately this work was incomplete and breaks a lot of our lore content, so the merge was reverted as it blocked 1.15 release.

Changelog:

• Changes the plague of undeath into an epidemic
• Adds new events for characters who come in close contact with the plague
• Contains fixes to the original work as well as long standing issues with the Scourge

Work still needed:

• Fix Scourge Vassalization event such that the Scourge vassalizes rulers overtaken by the plague
• Create events or effects that add troops to the Scorge in plagued counties (similar to original plague mechanic)
• Remove outdated plague mechanics code
• Fix start of Arthas events from Reign of Chaos and ensure that they fire consistently
• Ensure that the invasion of Quel'Thalas and tainting of the Sunwell fire consistently
• Reduce the plague type to Major from Apocalyptic; it is not a world-enveloping plague like Black Death
• Ensure that plague events do not fire across water if possible

Tests:

• Starting from 603 bookmark: Lordaeron should be plagued, Arthas activity should start soon after, all Arthas content should fire.
• Starting from 583 bookmark: Scourge should appear after Dark Portal is closed. Plagues should begin progressively across areas of Northrend ruled by mortal races.
• Starting from the 605 bookmark: Ensure that all relevant lore content is still working.
• There are no errors in wc files in Documents\Paradox Interactive\Crusader Kings III\logs\error.log except portrait_decals.cpp:101
• The mod takes less than 5.5 GB in the Task Manager (Windows)

[edmund-h]

note to developers:

• do not address the merge conflicts until work is ready to merge
• please do not add new content unrelated to the scourge, the plague, or any region infected by the scourge in this branch

[edmund-h]

arthas activity start fixed on dev