Improve DownloadData Extension to Deserialize to T

[Martin-Molinero]

Expected Behavior

• Being able to download and deserialize to T with helper method

Actual Behavior

• We download a string and later need to deserialize it to T. See https://github.com/QuantConnect/Lean.Brokerages.dYdX/blob/master/QuantConnect.dYdXBrokerage/dYdXBrokerage.cs#L440-L442

Potential Solution

Add new overload to deserialize to T

Reproducing the Problem

httpClient.DownloadData(url)

System Information

N/A

Checklist

• I have completely filled out this template
• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

• I have provided detailed steps to reproduce the issue