Update `Serializer` to have the same output latency with or without `flopInput`

### Motivation

The output behavior of `Serializer` changes based on whether `flopInput` is set or not, which can make the component more difficult to use when a configuration is changed. It would be possible to drive the output immediately, and it would be nice.

### Desired solution

Make sure the output latency of `Serializer` is the same whether `flopInput` is high or not. Add some logic so that the first cycle out is a direct feed through, but the rest of the data is latched in.

### Alternatives considered

_No response_

### Additional details

_No response_