Please return the version id in the current_version for add-ons returned from the discovery API

[bobsilverberg]

In order to support the new way of accessing versions, which is by versionId, we need the discovery API to return the id of the current version inside the current_version object for each add-on returned.

This blocks #12581, so if it could be done soon that would be greatly appreciated.

[AlexandraMoga]

Verified fixed on -dev

Before:

After: