Support OTP for SSH communicator

#### Description

Probably it will be useful to be able to pass a function to communicator that will trigger requesting of a new credentials and then form a required sshconfig or just credentials side of it, so while communicator establishes connection it would call this function and receive the new credentials.

Or maybe there is another way - but I found no good interfaces to implement such strategy.

#### Use Case(s)

Our compute resource management system requires user to create new access request every time it's connecting via SSH to the allocated instance. While preparing builder plugin for it I found there is no easy way to regenerate sshconfig for new connection.

#### Potential configuration

```
&communicator.StepConnectSSH{
Config: &b.config.Communicator,
Host: commFunc(host),
SSHConfigOtp: sshConfigFunc,
}
```

#### Potential References

As far I dug in - here is the place where sshconfig is used statically: https://github.com/hashicorp/packer-plugin-sdk/blob/main/sdk-internals/communicator/ssh/communicator.go#L346