[Measurement] Help tooltip does not update when mouse is not moved

[mbeckem]

Reproduction

• Open demo app and open the measurement component
• Click on the map to start measuring, but do not move the mouse

Expected Result

• Help tooltip updates to indicate that double click can be used to finish measuring

Actual Result

• Tooltip does not update (only after first pointer movement)

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Note: Also happens when finishing the current graphic via double click. The MeasurementController also needs to react to sketch start / finish / abort when computing the help tooltip.