layers: Encapsulate SEMAPHORE_STATE member data

Make all non-const member data private and restructure semaphore
tracking to allow it to eventually be made thread safe. The
biggest change is that each semaphore's state now keeps a
queue of pending operations, which removes the need to
frequently walk all pending submissions in every queue.

Fixes KhronosGroup#3590, which was introduced when one the 'for every queue'
loops was removed in a previous commit.

This change also adds checking for:
VUID-VkAcquireNextImageInfoKHR-semaphore-01781
VUID-vkAcquireNextImageKHR-semaphore-01779