Fix: ScrollArea repeatedly appears and disappears quickly issue. + For scroll_with_delta() + inner_margin

[rustbasic]

Fix: ScrollArea repeatedly appears and disappears quickly issue. (#4658)

• Closes #4658

If the mouse is at a specific position above the ScrollArea (in TextEdit?), the ScrollArea repeatedly appears and disappears quickly. You can more easily find the issue if you set Full bar width to the maximum value of 32.

If there is a better way to fix this than the solution in this Pull Request, please revise it accordingly.

AND

Fix: scroll_with_delta() for ScrollArea::vertical() and ScrollArea::horizontal()

• Closes #4584

We need to do this in order for ScrollArea::vertical() and ScrollArea::horizontal() to work even where they are divided or nested.

AND

inner_margin also applies to floating scroll.

• Closes #4664

[emilk]

Don't open multiple PRs with the same functionality. You have three options:

• Wait for https://github.com/emilk/egui/pull/4658 to be merged
• Use https://github.com/emilk/egui/pull/4658 as a merge-target for this PR
• Remove the duplicated commits