Investigate how to completely disable the builtin QML code model (and the effect of it)

The goal is that all functionality is provided by the LSP (to provide a similar experience in all IDEs, and because having two competing code models running at the same time is a waste of resources).

his is currently not possible. Partially because the LSP can't do everything the old code model supports, for instance refactoring actions. But partially also for accidental reasons caused by how things are implemented.

We should investigate ways to completely disable the old code model, initially only to compare what functionality we'd lose. Doing this "for real" will probably cause issues for QDS and MCU support, so that part is out of scope.