* Basic DHCPv6 UT framework.
* Add test cases for eGetDHCPv6State
* Add reset test case
* Add test cases for solicit happy path.
* Refine test flow
* Add test cases for advertise.
* Add final timeout & test case on waiting reply.
* Add DHCP address lease unit test case
* Add test case for socket creation failed.
* Disable debug print
* Fix coverage scan
* Add test cases for wrong msg type & transaction ID.
* Add more error handling case.
* Add test cases for prvIsOptionLengthValid
* Rename test case
* Add test case for prvDHCPv6_handleStatusCode
* Add test cases for vDHCPv6ProcessEndPoint_HandleReply
* Add test case for xDHCPv6ProcessEndPoint_HandleAdvertise
* Add test case for xDHCPv6ProcessEndPoint_HandleState
* Refine again.
* Refine again.
* Remove fall back function, not implemented for IPv6.
* Remove unnecessary check
* Add expect state mismatch test.
* Add test cases for create/close sockets.
* Add error handling and UT
* Ignore unknown sub-option.
* Add coverage for prvStateName
* Fix corner case for sub-option.
* Fix spelling & build
* Code beautify and remove unnecessary define
* Remove list_macros.h in DHCPv6 unit test.
