enable Tls 1.2 on Windows 7

[wfurt]

This is follow-up on https://github.com/dotnet/core-eng/issues/15558 and related to dotnet/runtime#67935
There was change in Helix to enable all protocols via registry since were able to get approval for that.
However Tls .12 is still not working on Windows 7 and we are failing to connect to external sites.
Unlike other Windows versions, Windows 7 needs additional setting to make it work.

https://support.microsoft.com/en-us/topic/update-to-enable-tls-1-1-and-tls-1-2-as-default-secure-protocols-in-winhttp-in-windows-c4bd73d2-31d7-761e-0178-11268bb10392
We will also need to add DisabledByDefault=0 for both Client and Server.
AFAIK it is ok to add that for all Windows if that is easier than just adding it for Windows 7.

[MattGal]

https://dnceng.visualstudio.com/internal/_git/dotnet-helix-machines/pullrequest/22625

[MattGal]

PR is merged and I verified (sample helix log) that I can access corefx-net-http11.azurewebsites.net from a Windows.7 Helix machine now. This should roll out next Weds (@wfurt FYI)

[wfurt]

Thanks @MattGal

[MattGal]

This rolled out today, closing.