vulkan: Add vkGetGlobalExtensionInfo entrypoint

vulkan: Add vkGetGlobalExtensionInfo entrypoint

have loader use it to enumerate all extensions from layers and drivers.
Non-gode_gen layers also updated to include vkGetGlobalExtensionInfo

Includes verion info as part of GetExtensionSupport return data.

TODO: vk-layer-generate needs work

v2: do not check for non-existing ENABLE_WSI_X11 (olv)