Available Views scrollbar position should be reset when switching traces

[PatrickTasse]

If you open a trace with many Available Views and scroll down to the bottom of that list, then open another trace which has less Available Views, the scroll bar is left in an out-of-range position for that list and the Available Views appears empty, which can confuse the user.

If you do this in the opposite order, the Available Views is initially in the middle of the longer list, although the scroll bar initially appears to be at the end of its range.

When opening a new trace the Available Views should always be initially at the top of the list.

When switching between already opened traces, ideally the scrollbar position would be preserved for each individual trace, but this is a nice-to-have.