kvm: Remove x86 cpuid test

For some reason, the test fails now. AFAIK, it is not the result of any
changes we've made since its inclusion. I've checked rust-vmm and it
appears that its respective cpuid test also fails now.
memory: Move includes in addres.hpp out of namespace

Unused/unfinished public using declarations are also commented out.
memory: Add FileOffset back
memory: Remove redundant comments for GuestAddress/MemoryRegionAddress
memory: Make GuestAddress' type aliases public
memory: Add checked arithmetic methods for Address
memory: Add FileOffset
memory: Add MemoryRegionAddress and change return type of the align method
memory: Add address tests
memory: Remove unecessary type aliases in GuestAddress
memory: Fix GuestAddress' align operation

The bitwise NOT operator in C++ is ~, not !.
memory: Address::align_up -> Address::align
memory: Remove unecessary methods from Address
memory: Mark checked_align_up as override
memory: Add & and | operators for Address
memory: Remove GuestAddressValue in public header
memory: Initial Address/GuestAddress pass
virtio: First pass at implementing virtio descriptors

For now, GuestAddress is in the same file, but should later on be moved to a
dedicated memory module
virtio: Setup
kvm: Fix kvm::device -> kvm::Device