Replace the implementation of how the roundtrips are done in
Wayland with one that is provided by the native Wayland client.

Additionally, fixes a small issue present in the Wayland swapchain
where WSI allocator would be freed by the destructor before
wsialloc_new was called resulting in an crash where WSI allocator
would be in an invalid state.

Change-Id: Idfadb88078f94ff15c9f18d1809b01941f2f8548
Signed-off-by: Normunds Rieksts <normunds.rieksts@arm.com>