Future-proofing McuSupport plugin against breaking changes

The coming Qt for MCUs version 2.0 is bringing breaking changes in the structure of the json files that existing versions of Qt Creator does not know how to parse. Specifically, the move from environment variables to cmake variables for 3rd party dependencies: Existing versions of the plugin do not have the functionality to create said cmake variables.

There is already some code that detects the version of the SDK and takes different code paths for legacy versions. There is however no code to decide to skip creating kits if the SDK version is above certain threshold. In other words there is a "min SDK" concept, but no "max SDK" concept.

The task here is to add a new field in the kit json files distributed with the SDK: "minQtcVersion".

The plugin should check that against the version of QtCreator it's being run on, and stop with an error if not met.  This will not solve the current situation with the breaking changes for existing versions of QTC, but will help future-proofing new versions of QTC against more future breaking changes coming from the SDK.

Acceptance criteria

• All kit json files distributed with Qt for MCUs 2.0 include a "minQtcVersion" field.
• The McuSupport plugin is able to read that value and emit an error if its own version is not high enough