Pass resource provider information to master as part of UpdateSlaveMessage

We extended UpdateSlaveMessage so updates to an agent's total resources from resource providers are possible. We realized that will need to explicitly pass resource provider details (here for now: ResourceProviderInfo) to the master so it can be queried for the providers present on certain agents. This should happen as part of UpdateSlaveMessage so a single synchronization channel is used for this kind of information.

We need to adjust UpdateSlaveMessage for these requirements. This should happen before 1.5.0 gets released so we do not need to deprecate a never really used message format.