[gamenetworkingsockets] Add new port

[Balnian]

Describe the pull request

Adds a port for Valve's GameNetworkingSockets

• What does your PR fix? Fixes #

Adds a port for GameNetworkingSockets
(finishing @aiusepsi great original PR #13312)

• Which triplets are supported/not supported? Have you updated the CI baseline?

x64-windows and x86-windows are supported
arm64-windows, arm-uwp-static, x64-uwp, and x64-windows-static are not supported

• Does your PR follow the maintainer guide?

It should?

[PhoebeHui]

Thanks for your contribution!

[BillyONeal]

This port is trying to use features to express alternatives -- the libsodium vs. openssl backends. Unfortunately using features to express this is inappropriate; the "north star" for features is that if port[featureA] and port[featureB] install correctly, installing port[featureA,featureB] needs to also work, but you have them paving over each other here.

As a result you'll need to choose one of the backends for this port as expressed in vcpkg. You can leave a comment for which changes would be necessary if someone wants to create an overlay-port that uses libsodium instead.

[BillyONeal]

This port triggered a team discussion because we have applied this "no feature alternatives" policy inconsistently depending on which maintainer was reviewing a given thing. The updates to docs are being done in #15171

[Balnian]

Sorry for the radio silence.
With what @BillyONeal said, that kind of helped me made the decision to drop the support for libsodium and refactor the port to only use OpenSSL as a dependency.

[PhoebeHui]

@Balnian, thanks for your updates!