feat: Add flag to force use of local control host address

[julianosk]

The assumption in the enterPassiveModeIPv4 function (in src/transfer.ts:48) is that NAT is only used if the "control connection" uses a public IP address and the "data connection" uses a private IP address.

However, in our particular scenario this is not the case. Both the control connection and the data connection use an private IP address but we are using NAT. The correct behaviour in this case would be to ignore the IP address mentioned in the PASV-response and instead use the control IP address.

To ensure we don't change current behaviour, we would like to introduce a configuration option that always uses the IP address of the control connection, regardless of whether the IP address is public or private. This configuration flag, called alwaysUseControlHost, is passed in the contructor and defaults to false.