kvm-unit-tests: VMX: The framework of EPT for nested VMX testing

The framework of EPT for nested VMX, including functions to build up
EPT paging structures, read/set EPT PTEs and setup a range of 1:1 map
EPT.

Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>
kvm-unit-tests: VMX: Test cases for nested EPT

Some test cases for nested EPT features, including:
1. EPT basic framework tests: read, write and remap.
2. EPT misconfigurations test cases: page permission mieconfiguration
and memory type misconfiguration
3. EPT violations test cases: page permission violation and paging
structure violation

Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>