Update CMake API version to 4.7

[Angais]

Summary

• Add 4.7 to the CMake GODOTCPP_API_VERSION choices
• Treat 4.7 as the latest bundled API version
• Keep older explicit versions using their versioned API JSON files

Fixes #2008

Checks

• cmake --log-level=VERBOSE -S . -B ../work/cmake-api47-final -DGODOTCPP_API_VERSION=4.7
• cmake --log-level=VERBOSE -S . -B ../work/cmake-default-final
• cmake --log-level=VERBOSE -S . -B ../work/cmake-api46-final -DGODOTCPP_API_VERSION=4.6
• git diff --check