AssumeUTXO: Block clock changes

[yashrajd]

It's become clear that loading assumeUTXO snapshot impacts the block clock (during IBD). Thus there is need to define and describe:

• how block clock is affected WHILE the snapshot is being loaded
• IF block clock should reflect/describe the progress snapshot loading given it is expected to take a non-trivial amount of time and the user cannot be expected to stay on the screen that shows progress inside of the loading user flow
• IF we choose to do the above, we should go through the logic and design changes first before touching code (comment)

Perhaps one solution can be to avoid tackling this altogether and show the progress in the assumeUTXO section or some other element on the landing screen.

This is an off-shoot of #79.

[GBKS]

Just seeing this. I posted a super simple design in the other issue. But, I did not consider the technical reality of this. My design simply treats the snapshot verification as a parallel process, which may not be the case. Let's find out.

[yashrajd]

Adding an example from my recent personal experience. Loading Sjors' signet snapshot, the only UI feedback (unintentional) is that my block clock shot to 54% quite suddenly ( I do not remember if it showed progress).