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/CMakeLists.txt

@@ -1,3 +1,30 @@
+include(FetchContent)
+
+FetchContent_Declare(
+  googletest
+  GIT_REPOSITORY https://github.com/google/googletest.git
+  GIT_TAG v1.16.0
+  GIT_SHALLOW TRUE
+)
+
+FetchContent_Declare(
+  catch2 
+  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+  GIT_TAG v3.8.0
+  GIT_SHALLOW TRUE
+)
+
+FetchContent_MakeAvailable(googletest catch2)
+
+# Force Google Test to link the C/C++ runtimes dynamically
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+
+# Disable building GMock
+set(BUILD_GMOCK OFF CACHE BOOL "" FORCE)
+
+# Do not install GTest 
+set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
+
 add_subdirectory(cpp_catch2_approvaltest)
 add_subdirectory(cpp_catch2_unittest)
 add_subdirectory(cpp_googletest_approvaltest)