fix: label arrays to be delimited by comma and add spaces for line charts

[zenocross]

Closes #12049

Line controllers apparently didn't have an overridden implementation for DatasetController's getLabelAndValue method.
Kept it within the line controller to not affect anything else.

[etimberg]

I'm not 100% sure that #12049 is a bug. @LeeLenaleee thoughts?

[LeeLenaleee]

I agree that it is not visually the most pleasing, but I don't think this is the correct fix.
Since we have a multi line label I think the more appropriate fix would be to multi line the title 🤔

[zenocross]

@LeeLenaleee Do you mean we'd want to modify the ', ' to an '\n' or is it something else altogether? Also, does the title text need to be centered?

Would be fine for a tooltip with a label with the following label array?
["Blue", ["subTitle", "hehe", ["test", "test2"]]]?