decide on starknet token and wallet address representations on cosmos

[rnbguy]

hermes-sdk has HasAddressType and HasDenomType but they have Display bound to use to_string() whenever possible.

But in Starknet, Felt::to_string returns the u256 number, not the hex encoded string which is mostly popular.

For example,

# u256
1311825980905418834733672785961618978053106732430637247341599459637071648036
# hex formatted. in python, this is just `hex(number)`
0x2e67799f855cff9fde57903a5c8ae4e31722c170d66203717c7756f366b1524

Ideally, we should use Felt::to_fixed_hex_string (for any kind of erc20 contract address) for the conventional hex format.