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Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

libsel4vm: Update documentation

This commit refreshes the interface documentation in libsel4vm.
This commit patches in missing documentation and additionally
ensures all interface documentation conforms to Doxygen style
comments.

libsel4vm: Made 'vm_memory_handle_fault' private

Made the interface function 'vm_memory_handle_fault' a private
function as this is only used internally within libsel4vm.

trivial: Style changed files

libsel4vm: Fixup includes and clean cmake file

Organise CMakeLists.txt file to be consistent with other projects.

libsel4vm: Remove guest_memory_arch_data

Removed the guest_memory_arch_data structure as this is no longer
used in the memory fault callback interface.

libsel4vm: Remove arch_data in mem fault callback

In the mem fault callback interface we replace the passing of the
guest_memory_arch_data interface with the faulting vcpu object.
Since we now have a vcpu fault interface we no longer need to
construct a custom datastructure to pass vcpu fault information.
The callback can rather query the needed information through the
vcpu fault interface. Updated the sources to reflect the interface
change.

libsel4vm: New guest memory interface

Developed a generic guest memory interface that can be used by
the x86 and arm vm implementations. This can be used to create
reservations in the guest vm memory and perform mappings on those
reservations.

libsel4vm: Refactored guest_vspace_touch

Removed vm_guest_vspace_touch out of the guest_vspace. This has
been reimplemented in a new interface, being 'guest_memory.h'.
Now called 'vm_guest_mem_touch'. Rather than relying on an
internal vm->vmm translation mechanism, vm_guest_mem_touch uses
the vspace interface 'vspace_access_page_with_callback' to
perform page accesses.