Add streaming support

System.Data.SqlClient (and Microsoft.Data.SqlClient) supports streaming binary data.

For example, here is how data can be streamed to the DB (untested):

let insertFile (connStr: string) (filename: string) (stream: Stream) : Async<unit> =
  async {
    let! ct = Async.CancellationToken
    use conn = new SqlConnection(connStr)
    do! conn.OpenAsync (ct) |> Async.AwaitTask
    use cmd =
      new SqlCommand(
        "INSERT INTO [File]
           ([Filename], [CreatedAt], [Data])
         VALUES
           (@filename, @createdAt, @data)",
        conn)
    cmd.Parameters.AddWithValue("@filename", filename) |> ignore
    cmd.Parameters.AddWithValue("@createdAt", DateTimeOffset.Now) |> ignore
    cmd.Parameters.Add("@data", SqlDbType.Binary, -1).Value <- stream
    do! cmd.ExecuteNonQueryAsync(ct) |> Async.AwaitTask |> Async.Ignore<int>
  }

Also, here's how to stream data from the DB (untested):

let getData (connStr: string) (fileId: int) : Async<Stream option> =
  async {
    let! ct = Async.CancellationToken
    use conn = new SqlConnection(connStr)
    do! conn.OpenAsync (ct) |> Async.AwaitTask
    use cmd = new SqlCommand("SELECT [Data] FROM [File] WHERE FileId = @fileId", conn)
    cmd.Parameters.AddWithValue("@fileId", fileId) |> ignore
    use! reader = 
      cmd.ExecuteReaderAsync(CommandBehavior.SequentialAccess, ct)
      |> Async.AwaitTask
    match! reader.ReadAsync(ct) |> Async.AwaitTask with
    | false -> return None
    | true ->
        match! reader.IsDBNullAsync(0, ct) |> Async.AwaitTask with
        | true -> return None
        | false -> return reader.GetStream(0) |> Some
  }

Would it be possible to add support for this to SqlClient? (Note, IMHO this is a "nice to have" feature that should be prioritized below e.g. #348).

I realize that reading is partly possible if using the DataReader option, though one must still check for nulls and access stuff by column index (like I have done above) or string name, so it would be nice to have that strongly typed, too.

Start with SqlClient's existing DataReader option and the System.Data.SqlClient/Microsoft.Data.SqlClient streaming documentation linked in the issue. Define the typed API needed for streaming binary data into and out of the database, including null handling and named or strongly typed columns; done means both directions are supported and covered by tests.