Only calculate and render things that are actually visible

[BridgeAR]

Feature request

Description

As a user, I want rendered being fast while keeping the memory overhead low so that I am able to load big maps and have a good user experience.

To do so, only the current metrics should be calculated and rendered, not all of them as it's currently done. As soon as a user would switch a metric, only the single metric needs recalculation. The other metrics would be calculated in the background as soon as the map is fully loaded and no other work is required.

Acceptance criteria

• Only changed metrics are recalculated
• Only the used metrics are initially calculated
• Lazy calculate the not initially used metrics in the background after loading the map