Adds initial support to the headless and Wayland backends to query
swapchain timing properties. This patch also moves all present timing
backend specific code into its own file and refactors the private_data
code that is specific to present timing entrypoints into a more common
format.
Change-Id: I377197a6e14b3cbd968e35735d43060d19dfe5bc
Signed-off-by: Normunds Rieksts <normunds.rieksts@arm.com>