This cl adds Buffer, BufferView and DeviceMemory.
- DeviceMemory contains the appropriate logic to allocate and map
  device memory.
- Buffer simply wraps a DeviceMemory and an offset for now.
- BufferView wraps a Buffer with a memory region and a Format.

Bug b/118383648

Change-Id: I6d53b9f0728d4cdec2696339cc6aa8ce2e05ca49
Reviewed-on: https://swiftshader-review.googlesource.com/c/21728Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>