[MU4 Issue] 'Collapse all instruments' should always scroll instruments into view

[avvvvve]

Issue type

UI bug (incorrect info or interface appearance)

Bug description

Followup from #19995

On MacOS (but should test on others), when scrolled mostly but not all the way to the bottom of the instruments panel with all instruments expanded, clicking 'Collapse all instruments' should not leave any space below the last instrument in the list.

Results vary based on scroll position. Sometimes, you see some of the last instruments at the top of the list, but there's still a big block of empty space below (see the first attempt in the attached video).

Any time that empty space would appear, it should place the bottom of the list at the bottom of the view.

Steps to reproduce

1. Add many instruments to a score (the Symphony Orchestra template is enough)
2. Click the ... options button at the top of the Instruments panel
3. Click 'Expand all instruments'
4. Scroll the instruments panel about 75% down
5. Reopen options, click 'Collapse all instruments'
6. See that there is extra space below the last instrument

Screenshots/Screen recordings

instrument-collapse-scroll.mov

MuseScore Version

From PR: #19995

Regression

No.

Operating system

macOS 14

Additional context

No response