logic: reduce access to filesystem while indexing

* use canonical filepath cache in cxx indexer
* made constructors of FilePath explicit
* use FilePath at more places instead of string
* forward declares FilePath wherever possible

src/lib_cxx/data/parser/cxx/ASTActionFactory.h

@@ -4,6 +4,7 @@
 #include "clang/Tooling/Tooling.h"
 
 #include "data/parser/cxx/ASTAction.h"
+#include "data/parser/cxx/cxxCacheTypes.h"
 #include "utility/file/FileRegister.h"
 
 class ASTActionFactory
@@ -11,7 +12,12 @@ class ASTActionFactory
 {
 public:
 	explicit ASTActionFactory(
-		std::shared_ptr<ParserClient> client, std::shared_ptr<FileRegister> fileRegister, bool preprocessorOnly);
+		std::shared_ptr<ParserClient> client,
+		std::shared_ptr<FileRegister> fileRegister,
+		std::shared_ptr<FilePathCache> canonicalFilePathCache,
+		bool preprocessorOnly
+	);
+
 	virtual ~ASTActionFactory();
 
 	virtual clang::FrontendAction* create();
@@ -19,6 +25,7 @@ public:
 private:
 	std::shared_ptr<ParserClient> m_client;
 	std::shared_ptr<FileRegister> m_fileRegister;
+	std::shared_ptr<FilePathCache> m_canonicalFilePathCache;
 
 	bool m_preprocessorOnly;
 };