Move CookieSecureOption / SecurePolicy to Http.Abstractions

[Tratcher]

This enum controls the behavior of the cookie secure option. We're going to add the same option to Session, so consolidate the enum down to Http.Abstractions.
https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.CookiePolicy/SecurePolicy.cs
https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNetCore.Authentication.Cookies/CookieSecureOption.cs