In preparation for viewing alerting and ML events over time in the inventory view, this ticket adds a timeline UI element to the bottom of that view.

Acceptance Criteria:

• Timeline view added to bottom of the view fixed to the bottom edge of the screen (waffle map will resize and become scrollable if necessary)
  • Collapsed by default, can be expanded and collapsed
• Saved view picker moved to top left corner under filters
• User cannot choose a time range or bucket span, these values will be pre-decided based on metricset.period
• Single line appears, charting the selected metric's overall average over this time range
• Clicking on the timeline changes the point in time value for the waffle map and readjusts the timeline so that the selected point in time is on the right edge
• If possible: Anomaly events appear on the timeline as red vertical bars

Not in scope for this ticket:

• Editable time range and bucket span (maybe we never need this?)
• User can select a node in the waffle map which will cause that node's metric values to appear in the graph below alongside the overall average (this causes the node above to display a "selected" state, represented by a black outline in the mockup)
• Alerting events in timeline
• Anomaly/alert states represented in the "waffle map" view (colored circles/squares)