[WIP] Military ECS Migration

[benjaminmcq]

this is very much WIP

this draft pr is so that every time i make a change, i won't lose it and other people can review and contribute as well to it instead of a bunch of file posting every time i finish and want someone to review it

i will add TODOs in the comments and code as i go

[benjaminmcq]

1st TODO list
self contained - no stubs needed

• terrain modifiers (i'm working on this)
• leader trait system
• unit type definition data
  mostly self-contained (needs a few stubs)
• deployment / OOB loading
• systems / scheduler wiring
  heavily dependent (mostly stubs)
• leader creation logic

note: these are the bigger things we need to implement, not quite everything
Implemented
create_regiment/create_ship
create_army/create_navy
recompute_group_stats
(most base non-method structures)

[benjaminmcq]

btw, sorry for the mangled commit