Improve test_minimal

[rsodre]

• Make the test_minimal tests more realistic using an actual deployed mock contract
• Instead of using contract_state_for_testing (), deploy MinimalERC721Mock and use its dispatcher, based on Testing Smart Contracts
• MinimalERC721Mock has a minimal interface, with mint() and burn(). Use dispatchers derived from the erc721 and nft_combo interfaces, and make sure we can call all public functions, like owner_of, token_uri, contract_uri, total_supply(), royalty_info(), etc.
• Make sure it's impossible to call protected functions from a made-up interface containing those functions, like _mint_next(), _set_max_supply(), _set_default_royalty(), etc.
• Avoid adding additional dependencies like snforge_std. If not possible, we must wait until Dojo is compatible with snforge, and port the Dojo examples tests to it.