Rename Qt-CMake-toolskits.json

The name of our Qt kits JSON file, Qt-CMake-toolskits.json is problematic for several reasons.

1. We should avoid upper case characters just to get a whole class of potential file system problems out of the way. Yes, even in 2023.
2. "toolskits" is not a word. The original file is called cmake-tools-kits.json. It contains the kits of the extension cmake-tools.

Following that pattern, and taking VSCODEEXT-49 into consideration, we should call the file just qt-kits.json.