vulkan/wsi/x11: Destroy Present event context when destroying swapchain

vulkan/wsi/x11: Destroy Present event context when destroying swapchain

Without this, the X server may accumulate stale Present event contexts
if a client creates and destroys multiple swapchains using the same
window.

v2: Based on Chris Wilson's review:
* Use xcb_present_select_input_checked so that protocol errors
  generated by old X servers can be handled gracefully
* Use xcb_discard_reply() instead of free(xcb_request_check())
v3: Rebased on top of this code having been refactored out of anv

Reviewed-by: Dave Airlie <airlied@redhat.com>