windows: add GetIfTable2Ex, GetIpInterface{Entry,Table}, GetUnicastIpAddressTable

GetIfTable2Ex retrieves the MIB-II interface table.

GetIpInterfaceEntry retrieves IP information for the specified interface.

GetIpInterfaceTable retrieves the IP interface entries.

GetUnicastIpAddressTable retrieves the unicast IP address table.

Change-Id: If9f619cb48da204da3bac8b429b3231432337b0a
Reviewed-on: https://go-review.googlesource.com/c/sys/+/744880
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>