Make horizon sync resumable for outputs

[SWvheerden]

Currently horizon sync is not resumable for outputs, it needs to be.
Although some parts of the horizon sync is resumable like the kernels, if the horizon sync times out or looses its sync peer during the output download it starts over from 0.

As the blockchain gets older and the outputs increase this becomes more and more difficult to do in a single pass.

[SWvheerden]

An idea we can implement is to somehow save the target hash + height, and just try and resync to that if its still in the main header chain.