Migrate Unit Tests to Dotnet 5

[Ez2Raven]

• Migrate Newtonsoft.JSON to System.Json for better performance.

• Restructure code to let controller layer handle Json Serialization/deserialization.

[Ez2Raven]

Performance profiling on a trivial implementation for processing SNMP json structures:

For a flat object with 3 properties, locating the last element

Deserialize Json string to C# Object for post processing = 110ms Parse Json String to JsonDocument and process each element = 40ms

In terms of performance, we should choose to work with JsonDocument instead of C# Object. However, working with C# Object also means that we have flexibility to work with other data structure such as Binary and XML.

For now, I will migrate to C# object processing until there's a need to tune performance.