Merge: json: move up general services, support Byte and more

Merge: json: move up general services, support Byte and more

This PR is a general clean up of the `json` package to prepare the support of two new serialization engines, add small new features and fix some issues in code. It should not change its behavior for existing clients.

* Move up some general deserialization services from `json` to `serialization` in order to make them available to other engines. This includes the class name manipulation services and safety services controlling which types are deserialized, including `class_inheritance_metamodel`.

* Support writing and reading `Byte` as either a plain JSON string or a special object with metadata.

* Support reading `Char` and `Byte` from plain JSON input using simple heuristics.

* Test the deserialization of plain generated JSON and fix a typo in the tests.

* Fix other minor issues in code.

Pull-Request: #2538