Task Updating on workflow page mistakenly reorders tasks

[jluethi]

The new way of updating tasks to a new version on the workflow page leads to them being reordered. Any task that is updated is moved to the end of the workflow sequence. I guess that's a side-effect of changing reordering logic & switching away from index-based inserts.

Tested on fractal-server 2.7.0, fractal-web 1.9.0-a4

It's a pretty bad bug though, because it breaks workflows in confusing ways after updates. Let's prioritize finding a good fix to go back to the old behavior (update a task => its position in the workflow sequence doesn't change).

Before:

After: