Flint: Create a custom time curve plot

This MR provides a dedicated TimeCurvePlot for the regulation.

• The time have to be provided as an epoch is second in UTC (time.time())
• The x-axis is displayed as datetime in local timezone
• Data transfer (bliss->flint) only use the diff
• Flint manage the amount of data displayed (which can be changed by the user)
• The default amount of data displayed is 2 minutes
• The autoscale can be temporarily disabled to allow to zoom on a part of the plot

This plot is a custom plot like others so can be used in other contexts.

See also #2800 (closed)