gRPC Batch Update to offer transaction capabilities

[ghost]

Is your feature request related to a problem? Please describe.
There are use cases where a client might need to update many records simultaneously and guarantee the atomicity of the operation, i.e. that all records are updated, or none if there is an error in any of the updates.

Describe the solution you'd like
Create a new batch record update gRPC interface that ensure that all updates are applied in one transaction.

Describe alternatives you've considered
There is no easy alternative to building the feature outside Open Saves.

Additional context
Add any other context or screenshots about the feature request here.