add Mavftp service, read-only for now

[Williangalvani]

This will help #457

thanks @ES-Alexander for the help =]

This adds a mavftp folder under ardupilot_logs

we should probably fix https://github.com/ArduPilot/ardupilot/issues/23339 or just disable it if a navigator is running.

this is a heavily modified of https://github.com/ArduPilot/MAVProxy/blob/master/MAVProxy/modules/mavproxy_ftp.py I added a fuse layer for it to work with the filelbrowser, and tried to better encapsulate functionality.

That said, I hate it. but it works. I still think we should probably move this to a dedicated rust service later on.

I thought of using mavlink2rest, but I'm worried about the performance of assembling the arraybuffers from the jsons. That would also go against my idea of upstreaming this to ardupilot eventually.

This could be further cleaned, but I'll open it for review to double-check this is path we want to follow.

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[Williangalvani]

changed it so it gets code from pymavlink directly. currently WIP as we wait for the PR to be merged over there