Add more spans for live updates; change when we early return from buffered events

[kegsay]

• Add more spans to live updates to account for more time spent in various functions.
• When there are a lot of stacked updates in the buffer, return after processing 100 of them rather than relying on >=50 list operations. List operations isn't a good proxy for the amount of work being done, as the majority of work updates are things like: receipts, typing, device list updates. This means we will return faster than before when we have stacked updates, reducing perceived latency, despite having to still go through the entire buffer.