TCP Keep-Alive OS and TFM targeting

TCP Keep-Alives is useful and required by customer and users, however, the implementation varies from platform to platform and TFM. This ticket is to propose that we

• Use IOCTL on all windows hosts as this is the best coverage in terms of implementation as all Windows OS's support setting it this way.
• Use SetSocketOptions on all non-windows platforms as IOCTL is a Windows specific implementation.
• Use TFM targeting for SetSocketOptions as its support is not tied to a .NET Standard but to .NET Core 3.0 or greater.