[cssom-view] Option to set a maximum amount of scrolling for behavior:smooth

This is about scrollIntoView usage.
In a use-case of mine I wanted to override a smooth scrolling behavior to instant if the amount to be scrolled was bigger than a certain amount of pixels. This is to avoid visual glitches and unnecessary processing. I ended up doing it myself with javascript: Basically check how much the scrolling would be and if it goes beyond a limit then set behavior to instant, otherwise let it be smooth. A new argument to scrollIntoView could be introduced to set a number to specify this. I'm not sure if this is already something that happens internally, so this might not be necessary with sane defaults.

Start with the CSSOM View specification's scrollIntoView definition and the issue's proposed maximum-scroll amount for smooth behavior. Determine whether the proposed option is needed and define the expected switch between smooth and instant scrolling; done means the behavior and API change are specified clearly enough for implementation.