[Performance] Only rerender changed elements

[JulianAssmann]

Currently, if a single argument changes in the configuration, the entire gauge is rerendered. E.g. every time the value changes, not only the pointer is updated, but all axes, segments, ticks, etc. are rerendered. This is obviously very resource-intensive.

Splitting the rendering of different elements like the segments, ticks and pointers to different render elements like RenderRadialSegment, RenderRadialTicks and RenderRadialPointer and only rendering after changes might improve the performance. Currently, all elements are rendered by a single RenderBox:
RenderRadialGauge.