Consolidate multiple related notifications on the notification bar

[cobaltbeau]

This'd mainly be for DoWs, making peace, and city-state quests, as they are the ones that get stacked often.

Basically, instead of 9 different notifications for the start of a war between two civs with several suzerains each, combine the text from all into a list on a single notification.

However, with this system, it might be difficult to pick out the actual civs from among of city states,
to which I have 2 possible solutions:

1. Color code the cities, with different colors for you + your joint war partner (if you have one) (1 color), either of your CS's (2 colors), the enemy civs (3 colors), and their CS's (4 colors)
2. Instead, replace the notification text with "Russia (+3 city states ) has declared war/made peace with Arabia (+2 city states).

[chaorace]

I think the best implementation for this would be adding horizontal stacking and sorting notifications into these stacks based on type.

I'm thinking something like this: by default, they would be scrunched up, similar to how district icons in the city banner look, but would expand to full width on mouseover. Something like this would be lower in implementation cost, and, at least in my opinion, is more immediately intuitive

[chaorace]

This is being handled as part of #514