option to scroll to the top of the next cell

[amunger]

for #191086

new options for scrolling behavior:

• Scroll to fully reveal the next cell. (current behavior, and using as default for now)
• Scroll to reveal the first line of the next cell. (requested in the linked issue)
• Do not scroll at all. (requested in this comment)

After people have been able to experiment, I imagine we will change the default to the second option.

[rebornix]

Let's use viewContext.notebookOptions.getLayoutConfiguration() for calculating the padding instead of constants.

[NickCrews]

Thank you @amunger, I just got this feature in the newest version and the "do not scroll" option is finally what I have been looking for! 🙏