Default CMake generator

Generator should be picked from cmake.generator setting as it works for CMake plugin.

Default generator selected: Ninja Multi-Config. The reasoning:

• Keeps MSbuild and Xcode generators configurable.
• Resolves switching between configuration without deleting build folder on the VScode with default settings.
• Faster switching between configuration and build resources sharing between configurations.
• Automatic Multi CPU cores utilization.
• Top build performance.
• It is in Qt bundle.
• Unification.

MSbuild and Xcode generators are multi-config generators. Multi-config generators have specific requirements to CMake files which are not detectable for non-multi-config generators. This may cause CMake-related configuration bugs.