CMake Debugger: group variables better

### Brief Issue Summary

See the image:

There are 52 local variables (already reduced from 140 by unsetting variables). So it is quite hard to find/see the variable I would be looking for.

So is there some way to group variables better (like the cmake gui does by `prefix_`) or to filter the variables in the debug view somehow? Alternatively showing variables only set by `CMAKE_CURRENT_LIST_FILE` and provide an expandable tree for the `CMAKE_PARENT_LIST_FILE` or variables set via `PARENT_SCOPE` from included/"child like" list files?

### CMake Tools Diagnostics

_No response_

### Debug Log

_No response_

### Additional Information

_No response_

No source file, test, or entry point is named in the issue. Start by reviewing the existing CMake debugger variable view and the requested grouping or filtering alternatives, then define one concrete behavior and acceptance criteria before locating the implementation. Done means the debug view presents CMake variables in the agreed grouping or filtering scheme.

Written by the indexing model from the issue text.