* Fix `--stream` combined with `--format` for `jsonnet`
If both are defined and jsonnet defines a list, it currently only generates one of the resources
Also added a test for it
* Minimize diffs by keeping all in one file
`extVars` are a concept of Jsonnet that allow to inject data into the compiler
from the command line.
At Grafana, we have a build-image whose tag must be consistent across all CI
systems, so we use such an extVar for this.
To be able to adopt drone-cli (were using plain `jsonnet` before) we need this
functionality exposed :D