Support empty projection in CSV, JSON readers

[Dandandan]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
As a user of the readers, I want to be able to use the CSV and JSON readers with empty projection.

Describe the solution you'd like

Support empty projections in the readers. The readers should generate a RecordBatch that returns a batch with the correct number of rows.

Describe alternatives you've considered

Additional context
In DataFusion I want to avoid scanning a column apache/datafusion#3214 . Implementing the support in the arrow readers seems the best and easiest way forward.