Add some pre_progress to Tails Cloner progress bar when partitioning

The progress bar should be more linear, especially when partitioning which adds 2 minutes. This MR adds some very coarse progress during that time that is very roughly proportional to how long partitioning takes compared to the extracting and rsync operations.

The total misc_progress added is 1 GB which is about half the time of the copying operation for cloning. (1/3 of the total progress is from partitioning).

I also removed some useless division by 1024 and had to move the max_progress calculation outside of the progress thread.

@sajolida: let me know if this is good enough UX. Any solution giving progress updates during the 90s slumber of partitioning and 30s slumber of formatting needs more complex code, this MR makes the code a little simpler to read than before.

Closes #20405.