Store enabled instance and device extensions

Store enabled instance and device extensions

Stores the enabled instance and device extensions during
vkCreateInstance and vkCreateDevice respectively. This fixes an issue
where function pointers for functions of disabled extensions were
returned during vkGetInstanceProcAddr/vkGetDeviceProcAddr.

Adds functionality for adding extensions that belong to a subset of
other extensions in util::extension_list.

Adds function for checking if the proper surface extension has been
enabled in each WSI backend.

Signed-off-by: Iason Paraskevopoulos <iason.paraskevopoulos@arm.com>
Change-Id: If5e23e0d07c9f09006be18c410c4e1d4c3a1e676