NpgsqlDataAdapter doesn't support batches

Attempt to set `NpgsqlDataAdapter.UpdateBatchSize` fails with `Specified method is not supported.`.
This implementation inherited from [DbDataAdapter.UpdateBatchSize ](https://docs.microsoft.com/en-us/dotnet/api/system.data.common.dbdataadapter.updatebatchsize?view=netstandard-2.0). 
Is it possible to implement batch support similar to `SqlDataAdapter`?

