Emit "in combat" lines from the ffxiv plugin itself rather than OverlayPlugin

[quisquous]

fflogs could use the "in combat" lines that OP emits, but it's not helpful if OP the one emitting them. It'd probably make more sense to move them into the ffxiv plugin itself if possible.

I was thinking about this discussion in discord the other day, and wanted to write it in an issue so it didn't get lost. See: https://discord.com/channels/551474815727304704/594899820976668673/1108547438479933470