insights view for multiple targets data

Right now, we only have an insights view per target. Since people use targets to model different stages of their deployment (e.g. dev, staging, production, etc.) and we already use usage data from multiple targets for the breaking change detection, we should think about also having a view that shows the operations/usage data from all/selected targets.

Example table header:

```
operation name | client names | target names | request count | error counter | ...
```

It would also be nice if we could filter that list based on one or more of the following criteria:
- operation name(s)
- client name(s)
- target name(s)
- schema coordinate(s)