Fix vertical alignment when jumping from multibuffers (#22613)

Clicking buffer headers and line numbers would sometimes take you to a
disorienting scroll position. This PR improves that so the destination
line is roughly at the same Y position as it appeared in the
multibuffer.



https://github.com/user-attachments/assets/3ad71537-cf26-4136-948f-c5a96df57178


**Note**: The alignment won't always be perfect because the multibuffer
and target buffer might start at a different absolute Y position
(because of open search, breadcrumbs, etc). I wanted to compensate for
that, but that requires a fundamental change that I'd prefer to make
separately.

Release Notes:

- Fix vertical alignment when jumping from multibuffers