Restructure build targets of CMake configuration

* Rename the library under test from src to GildedRoseLib.
* Move the lib folder to test/third_party and handle ApprovalTests.hpp as header-only dependency.
* Remove the superfluous googletest_approval_main.cpp (in the same sense as there is only one GildedRoseCatch2ApprovalTests.cc)
* Set USE_FOLDERS property such that target ALL_BUILD, RUN_TESTS and ZERO_CHECK are grouped for Visual Studio.
* Set WORKING_DIRECTORY such that the RUN_TESTS target works successfully.
* Fix C++ language standard for Catch2 v3 to C++14.
* Bump third-party dependencies
  * Update ApprovalTests.hpp to v10.13.0
  * Update Catch2 to v3.8.0
  * Update GTest to v1.16.0

cpp/test/cpp_googletest_approvaltest/GildedRoseGoogletestApprovalTests.cc

@@ -1,8 +1,5 @@
-// Include header files for test frameworks 
-#include <gtest/gtest.h>
+#define APPROVALS_GOOGLETEST
 #include <ApprovalTests.hpp>
-
-// Include code to be tested
 #include "GildedRose.h"
 
 std::ostream& operator<<(std::ostream& os, const Item& obj)