Make `Table` min/max_scroll_height Optional by default

[LeonardMH]

Changes the TableScrollOptions to use Optional values for min_scroll_height and max_scroll_height, requiring the user to call the respective builder functions if they desire those behaviors.

This addresses the surprising effect that by default Tables limit themselves to a maximum height of 800px (#3114).

Closes https://github.com/emilk/egui/issues/3114.

[LeonardMH]

I saw the contributing guideline to not open the PR from my master branch and assumed I would be able to edit it after opening the PR but I guess I can't. I have created a separate branch bugfix/tables-have-bounded-height-by-default in my fork if you'd rather work from that.

[LeonardMH]

Need to update the relevant documentation / comments.

[emilk]

This will match how ScrollArea works, so I guess it makes sense. But no need for Option, just use f32::INFINITY instead, just like ScrollArea::max_height does

[emilk]

Check the docs for ScrollArea to see a bit more about why we have these settings.

[emilk]

Converted to draft awaiting progress