layer: improve how layer handles Vulkan extensions

layer: improve how layer handles Vulkan extensions

In vkCreateInstance:

- ppEnabledExtensionNames is checked to determine which window-system
  platforms the layer should enable support for.
- support in the layer is always enabled if possible, even if this may
  be provided by the ICDs. Platforms not supported by the layer should
  still be correctly supported by the ICDs (untested.)
- pApplicationInfo is changed to bump the Vulkan API version
  in order to enable instance extensions that are necessary for some
  of the platforms implemented in the layer.

In vkCreateDevice:

- ppEnabledExtensionNames is extended with device extensions required
  by the layer.
- if the extensions are not supported by the physical device, the
  layer fails to initialize the device.

Change-Id: Ibdd69fca38e7909d5b8f0ac7698805ea5f425ac6
Signed-off-by: Joe Jenner-Bailey <joe.jenner-bailey@arm.com>
Signed-off-by: Matteo Franchin <matteo.franchin@arm.com>