* Move "using namespace std;" from header to module file (to no longer pollute the global namespace).
* Fix inconsistency of having namespace prefix in test code.
* Add include guard to GildedRose.h.
* Avoid std::endl.
* Have consistent white-space.
* 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
