ProjectExplorer: Rename IncludePathType to HeaderPathType

It is the type used by the HeaderPath class, so reflect that in
the name.

I also considered to rename HeaderPath to IncludePath, but
that name is reflected in a lot of users, which would also need
to be adjusted for consistency. That would blow up the patch size
for little value IMHO.

Change-Id: I51421dbd3ab8b2874dc32fc82dc394c9b93ce5e9
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/cpptools/includeutils.cpp

@@ -535,7 +535,7 @@ static QList<Include> includesForSource(const QString &filePath)
     cmm->GC();
     QScopedPointer<CppSourceProcessor> sourceProcessor(CppModelManager::createSourceProcessor());
     sourceProcessor->setHeaderPaths({{TestIncludePaths::globalIncludePath(),
-                                      ProjectExplorer::IncludePathType::User}});
+                                      ProjectExplorer::HeaderPathType::User}});
     sourceProcessor->run(filePath);
 
     Document::Ptr document = cmm->document(filePath);