Contract fixes

[MaksymZavershynskyi]

Our contracts are missing the following important assertions:

• The Near fungible token should accept the address of the corresponding locker contract when it is initialized and it should verify that the proof to the event that it receives corresponds to the locker contract that it was initialized with;
• The Near fungible token should record hashes of the events that were used to mint and it should not allow the same proof to be used twice;
  • The code that sends the proofs to the fungible token should attach some tokens to account for the increase in storage;
• In Eth2NearProver contract the verification of the proof should be before the cross contract call to the client: https://github.com/near/rainbow-bridge/blob/c42defee097d2e4ac6d86777ae1c374e728402e1/libs-rs/eth-prover/src/lib.rs#L143 When skip_bridge_call == false we should be returning the result of the verification, and when skip_bridge_call == true the promise. Use PromiseOrValue<bool> for it, see: https://github.com/near/near-sdk-rs/blob/master/examples/cross-contract-high-level/src/lib.rs#L58