CMake: Replaced test-specific dynamic loader options

[M2-TE]

Here's an example of how VULKAN_HPP_TESTS_BUILD_ONLY_DYNAMIC could be replaced by the use of VULKAN_HPP_DISPATCH_LOADER_DYNAMIC, meaning I've only touched the testing side of things so far.

And looking at this, why are those tests disabled for dynamic loading? CI always enables VULKAN_HPP_TESTS_BUILD_ONLY_DYNAMIC at the moment, so they never get tested at all.

~Tests will still fail as the CI does not set the dynamic loader option yet, I'm waiting for #2110 to prevent any merge conflicts.~

[M2-TE]

@asuessenbach could you give the CI a little shove when you get the time? I can't seem to trigger it myself.