Redrawing the window contents for every possible event is not
a reasonable thing for an application to do. The test should be whether
redrawing on demand plus periodic updates works with near-idle CPU use
and no extra input latency.
This change incidentally makes the test well-behaved on Wayland, where
it was previously broken due to every EGL buffer swap causing an event
to be received.
This updates to a newer version of glad2 and switches to the header-only
variant.
This also (finally) switches to the newer glad2 loader signature that
allows us to pass in glfwGetInstanceProcAddress directly.
This removes all dependencies from the GLFW test programs on the Vulkan
SDK.
It also removes support for linking the GLFW shared library (dynamic
library, DLL) against the Vulkan loader static library.
