Add retention metrics to Builder

## 🎉 Description

The Data team has added retention metrics to the scene stats json: https://cdn-data.decentraland.org/scenes/scene-stats.json

```
"retention": {
"d1": number,
"d3": number,
"d7": number,
"d14": number,
"d28": number
}
```

We can make use of this data and show in the Builder for scenes and lands as we do now with the weekly stats:

Since we are already fetching the `scene-stats.json` we do have already this data in the builder in memory, it's just a matter of displaying it.

**BLOCKER:** We would need designs for this before implementation can happen