Better community treasury account derivation

[clangenb]

I suggest that we do something like: https://github.com/ajuna-network/ajuna-pallets/blob/develop/pallets/ajuna-tournament/src/account.rs

[brenzi]

We use an account derivation in faucet too, where we have existing accounts already. What would be the reasoning to change it (everywhere) with possible state migrations?

[clangenb]

The current one in the treasuries pallet seems a bit hacky to me, and the one I suggest makes it obvious (by string) if it is a treasury account, which can be nice for UIs. We could use the same and put the formatted CID in the account id string.