* Create system text serializer
* Assign property names with system text
* Use the new serializer
* Impement AutoInterningStringConverter with System.Text.Json
* Implement TextAutoInterningStringKeyCaseInsensitiveDictionaryConverter
* Make CaseInsensitiveDictionaryConverter
* Force datetimes to be read as UTC
* Remove usages of Newtonsoft.Json
* Remove text prefixes
* Remove unused Newtonsoft converter
* Remove more newtonsoft
* Remove duplicate implementation
* Rmove usage of missing class in tests
* Ignore null values
* Fix tests
* Remove Newtonstoft reference from NuCache
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Co-authored-by: Elitsa <elm@umbraco.dk>