Add json-qmlproject conversion for MCU nodes and properties

QDS converts the project representation between json and qmlproject whenever it needs to make change to the project file. Currently all MCU specific nodes and properties are dropped (ModuleFiles, TranslationFiles, MCU.Config etc) by this conversion.

This task will add the MCU specific qmlproject features to the QDS converters, and tests for the full requirements in the qtcreator repo under tests/unit/tests/unittests/qmlprojectmanager

We need to decide how to represent MCU features in the json format used by QDS before implementing the converter. TBD if a separate ticket is needed for this.

It would be good to keep the maintenance burden of adding new MCU properties/features in mind when designing the conversion