Add service graph connector to the OTel collector

Source: https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/connector/servicegraphconnector

Functionality

The service graphs connector builds a map representing the interrelationships between various services in a system. The connector will analyse trace data and generate metrics describing the relationship between the services. These metrics can be used by data visualization apps (e.g. Grafana) to draw a service graph.

Scope

Tech preview with tests and documentation. For now, we will enable Grafana integrations, but this clears the path to our own UI.

Also: Discuss with the UI team how to integrate in our own UI or if we can have something simple now, ideally contributing to already existing graphs. For example: "can we just add lines to existing graphs?". The requirement now is not to implement it in the console, but to understand which options we have so we open a follow up feature to visualize the services.