Fix slow Process table

[sbothma]

The Process table is unusable when the node is running many processes.

• avoid keeping process info for all processes in memory
• avoid .sort, .take, and .map on extremely long lists
• remains fast for hundreds of thousands of processes
• only slow (3s) showing 5000 processes out of hundreds of thousands

[josevalim]

Thank you for the PR @sbothma! Can you please look into failing tests? I also wonder if we should add Enum.take_sort to Elixir... although that's a separate discussion. :)

[sbothma]

This is still hitting a bottleneck somewhere around 200 000 processes. I'll split out the take_sort implementation. My goal here is to be able to have the Process table respond in less than a second (the minimum auto update rate). At least up to the default process limit.