Refactor metadata sources and decorations

[mariomac]

Wit the addition of docker metadata support #1190 and the future addition of VM/Cloud metadata (and others), I realized that the decoration pipeline is becoming more complicated and the different metadata are replicating some similar functionalities. This will lead to code being difficult and hard to maintain.

I propose unifying the decoration decoration nodes into a single one that will decorate traces and network data from diverse metadata sources (K8s entities, Docker container, Cloud metadata...)