Optimize polling data flow

[norbertsuski]

Summary

Current implementation has following issues with polling optimization which can be improved:

• one tile is fetching all data twice - once for summary and once for recent incidents, sometimes it is the same source of information that could be fetched once
• tile itself can fetch all data and than pass last incidents to small timeline on tile, instead of creating two Network objects to fetch data
• when opening big timeline, new polling process starts, which is getting the same data as tile
• when removing tile, data is still polled in background

Possible Solution

• [x] fetch data once and format as summary and recent incidents in main StatusPage component (if possible)
• [x] remove unnecessary Network object initialization in CurrentIncidents and pass incidents from StatusPage
• [ ] add possibility to handle onClose event when StackedNerdlet is closed which will allow to stop polling data
• [x] clear polling when user deletes tile