net: support TCP_KEEPIDLE, TCP_KEEPINTVL and TCP_KEEPCNT on newer Windows #65817
Description
In CL 542275, the implementation on Windows has a few limitations:
TCP_KEEPCNTis not supported.TCP_KEEPIDLEandTCP_KEEPINTVLcannot be set separately, they must be set together.
Lines 121 to 127 in ff4e45f
These limitations come from SIO_KEEPALIVE_VALS that is used for TCP keep-alive on Windows in Go currently. It's a relatively old Winsock API for setting up the TCP keep-alive mechanism. I've done some more in-depth research on Windows and realized that we can do more things on some relatively newer versions of Windows using setsockopt and getsockopt.
TCP_KEEPIDLE and TCP_KEEPINTVL are available starting with Windows 10, version 1709. TCP_KEEPCNT is available starting with Windows 10, version 1703. Therefore, we can reconcile the implementation on Windows 10, version 1709 and later versions with the implementations on UNIX's.
Follows up #65809