I read that only users and NNS canisters can hold ICP, and for this reason Wrapped ICP (WICP, caninster ID o5d6i-5aaaa-aaaah-qbz2q-cai
was invented.
It is still true that only users and NNS canisters can hold ICP?
If ICP is now freely movable between canisters, what is the ICP canister ID?