mcuboot: Use dedicated type for slot numbers#24753

tomchy merged 1 commit intonrfconnect:mainnrfconnect/sdk-nrf:mainfrom

tomchy:bugfix/mcuboot/NCSDK-35199_Remove_magic_numberstomchy/sdk-nrf:bugfix/mcuboot/NCSDK-35199_Remove_magic_numbersCopy head branch name to clipboard