[contracts] Balances are not updated when tokens are transfered

[Willgg]

Claim() and Cancel() do not update the balances of accounts. The variable _balances must be updated. As this update is done many times in this contract the update of balances must be refactored in a dedicated function.

v1-core/packages/hardhat/contracts/Swapper.sol

Line 91 in 96bc553

function claim(uint256 id) external override returns (bool) {

v1-core/packages/hardhat/contracts/Swapper.sol

Line 107 in 96bc553

function cancel(uint256 id) external override returns (bool) {