logic: Fixes and improvements for C/C++ compiler header path handling

* Always add compiler header path when prefilling on first start, regardless of successful detection
* Show compiler header path in path list box on top and readonly
* Prepend compiler header path on Windows in system header path compiler flags, append otherwise
* Show warning when saving ApplicationSettings if compiler header path is not in global include paths
* Show warning when saving ApplicationSettings if there is another path containing compiler headers

src/app/main.cpp

@@ -137,6 +137,8 @@ void prefillCxxHeaderPaths()
 		std::shared_ptr<CombinedPathDetector> cxxHeaderDetector = utility::getCxxHeaderPathDetector();
 		std::vector<FilePath> paths = cxxHeaderDetector->getPaths();
 
+		paths = utility::replaceOrAddCxxCompilerHeaderPath(paths);
+
 		if (!paths.empty())
 		{
 			MessageStatus(L"Ran C/C++ header path detection, found " + std::to_wstring(paths.size()) + L" path" +