Add ProtoIdeInfo for proto_library targets to TargetIdeInfo

[simuons]

Expose proto_library targets in TargetIdeInfo during sync via ProtoIdeInfo (similar to other *IdeInfo)

Motivation idea.plugin.protoeditor doesn't work for us (all imports are red/unresolved) because source roots of proto_library targets are not configured. Plugin's automatic configuration includes source roots for synced scala/java but has no knowledge about proto_library targets. It is possible to configure source roots manually but is not feasible because we have lots of small targets.

Would you be willing to add this? If so I could open a PR for it (I have a commit which adds ProtoIdeInfo)

My current approach to resolve proto imports is writing SyncListener which reads targets with ProtoIdeInfo and configures source roots to PbProjectSettings. I'd love to hear your insight how this should be approached. Is SyncListener correct place to achieve that? Or it should be implemented as BlazeSyncPlugin (maybe with additional_languages: proto)?

[liucijus]

Related issue #3214

[auzhva]

Hi. We're also using a lot of protobuf and suffer from same. Support for automatic deps configuration would be super-nice to have.