Add ability to subscribe to block data via grpc

[evan-forbes]

Per request from the node team, we should have an equivalent method to stream block data via grpc instead of only via rpc.

ref celestiaorg/celestia-app#3421 (comment)

[evan-forbes]

per sync: we should make sure that we are also updating the configuration for the max size. The default is ~4MB ref celestiaorg/celestia-app#3437

[Eoous]

Is it necessary to add ability to subscribe via grpc when it's able to get block data by hash or height?