CMake Project Manager: Support C++20 Modules

CMake master has CXX_MODULES and CXX_MODULE_HEADER_UNITS to be able to support C++20 Modules, together with compilers that already support scanning dependencies from paper P1689r5.

The feature is documented by CMake here and described in last CppCon talk.

To fully integrate this feature with IDE we should enforce BMI (Build Module Interface) regeneration each time after any of source file that "belongs to" module changes. This is the only thing that clangd doesn't do automatically and thats why it shows false-positives errors in current QtCreator (based on outdated BMI).