Enable VK_KHR_swapchain for instances.

This is a specific instance of a general capability.  Beginning with Vulkan
1.1, physical-device commands can part of device extensions, and can be called
before the application creates a device.  vkGetInstanceProcAddr only returns
commands for enabled extensions, and so we must internally enable device
extensions inside of the instance.  This commit enables VK_KHR_swapchain so
that GIPA will return vkGetPhysicalDevicePresentRectanglesKHR.

Bug: b/71744435
Test: Modified LunarG cube demo that can successfully GIPA the command.
Change-Id: Iefb9f82d3f21e110d45f7d6aae7c8c9ea3af20b9