* Provides an abstraction for creating the JavaScriptEncoder used in SystemTextConfigurationEditorJsonSerializer.
* Generalised JSON serialization encoder factory to work for all System.Tex.Json serializers.
Added the serializer's name as a parameter to allow for different encodings per serializer if required.
* Fixed tests by removing use of obsolete constructors.
* Removed name parameter and used a generic type instead.
* Add amount validator
* Add ObjectTypeValidator to MNTP
* Move validate startnode to helper method
* Validate allowed type
* Fix tests
* Added some XML header comments and resolved nit-picky warnings.
* Further XML comments.
* Fix null validation case
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Co-authored-by: Andy Butland <abutland73@gmail.com>