Use streaming to avoid allocating large string objects for JSON

[dbrattli]

We need to make sure we never allocate more than 85K for a single string or we will end up on the LOH. Investigate how we instead can stream JSON docs to/from CDF.

• https://www.newtonsoft.com/json/help/html/Performance.htm
• https://johnthiriet.com/efficient-api-calls/#
• https://github.com/MangelMaxime/Thoth/blob/master/src/Thoth.Json.Giraffe/ThothSerializer.fs