1. update to use 1 EFI Variable per NIC (instead of converge all NIC configuration...

1. update to use 1 EFI Variable per NIC (instead of converge all NIC configuration into one EFI Variable), this remove the limitation that max NIC configuration will depend on PcdMaxVariableSize.
2. remove unnecessary Unload function EfiIp4ConfigUnload (use default Unload function NetLibDefaultUnload instead), remove global array for NIC handle tracking since it’s driver model driver.
3. add Ip4Config Variable reclaim to HiiConfigAccess.RouteConfig() to remove variable for NIC which has been removed from the system.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10628 6f19259b-4bc3-4df7-8a09-765794883524