Configure extension command broken due to simulator.json

[radu-stefan-dt]

Describe the bug
simulator.json follows a different format than our other configurations - the datasources expect a list of objects, whereas regular config files work with 1 single object. As a side effect, when trying to configure an extension and the command parses the available files it will wrongly try to access simulator.json as an object when in fact it's a list.

For now, we can ignore simulator.json from the Configure extension command.

In the long run though, both types of configurations should be in sync (see #166)