Update C++ module guidance in line with upstream changes

As discussed in #299, #300, and #301, this issue tracks the massive changes to the C++ module in the past several months.

We are working on https://github.com/KhronosGroup/Vulkan-Hpp/pull/2358/ which changes the readme, and should be merged in some time next week. Shortly after, the guidance in the Vulkan Tutorial ought to be updated.

As for the experimental status, _personally_ I am very happy to lift it out once https://github.com/KhronosGroup/Vulkan-Hpp/pull/2443 is merged. The warning is really only there to account for compiler ICEs more than anything else, and non-CMake build systems are happy enough nowadays.

Read the changes described in upstream pull requests 2358 and 2443, along with issues #299, #300, and #301. After the upstream changes land, update the Vulkan Tutorial's C++ module guidance to match them and resolve whether the experimental-status warning should remain.

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