Retool Otto's story event chains

[zijistark]

Though the changes are mostly for SWMH, some affect both maps.

• [x] Completely rewrite de jure reassignment code for when Thankmar wins his rebellion on SWMH
• [x] Ensure Thankmar gets no claims on all the vassals he sets free
• [x] Otto should not form the HRE by event at all, and instead that code should be reflected in the HRE formation decision(s)
• [ ] Otto's free invasion of Italy should be either an emf_restore_hre CB or an emf_restore_hre_player CB — not a claim CB (and probably not even available to the player given the existence of these CBs)

I don't know enough about Otto's relationship with this allegedly traitorous Giselbert fellow to bother with that part of the story events.

[zijistark]

Eh, let Otto's Story invasion of Italy just be a claim CB. Accomplishes virtually the same thing. That completes this work item then.