Refactor image formatting, and allow supporting new image formats in a backward compatible way

[MabezDev]

cc: #701

This is quite a complex task, and we'll likely need to iterate a bit with the design here. Currently image formatting, is tightly coupled to the targets, which is then coupled to the flasher module. We need to find a way for elf inputs to be turned into the image format in a more self contained way.

In the meeting, we discussed some kind of API/Abstraction to take CodeSegments as an input, and then depending on the selected image format create an appropriate output. This was just a rough outline, and there is a lot of investigation and iteration needed to come up with a final solution here.