So I tested it, and of course this is just a 10 minute test, so take it with a grain of salt, but I made a very janky berry farm with 3 foxes and bone meal and it yields enough berries in a minute to make a toretoise grow the ores back, obviously there's a huge random factor here, both from the farm and the toretoise itself, but it works.
In terms of big farms with magnet/flying machine, I used the void world gen and planted berries in the spawn platform, and while it's not the biggest farm you could make, I have my doubts it could give enough food for the toretoise, but more test is needed in this case. (I just eyeballed it)
some notes I can provide is that the toretoise keeps eating the berries while in cooldown (probably everyone knew that) so only giving just enough food to grow the ores is the desirable choice.
