The Main Module Upgradeable is the main contract that holds the logic for the wallet. It is upgradeable, meaning that the logic can be changed without changing the address of the wallet. When the wallet is deployed, the MainModule is used as the initial code implementation. This module uses the counterfactual address of the wallet to validate the imageHash of the wallet configuration. When the wallet configuration is updated, the MainModule will automatically replace the wallet code implementation with MainModuleUpgradeable, while handling the storage initialization.