Windows: Start building Docker images for Windows 2025 in CI (but keep building images for Windows 2022 as well)

[DilumAluthge]

Each 2025 Dockerfile (Dockerfile.2025) was generated by:

1. Copy the contents of the 2022 Dockerfile.
2. Replace all occurrences of ltsc2022 ---> ltsc2025

Here is the specific script that I used:

for arch in ["x86_64", "i686"]
    cd("./windows/package-$arch") do
        contents = read("Dockerfile.2022", String)
        patterns = Dict(
            "ltsc2022" => "ltsc2025",
        )
        for (old_pat, new_pat) in patterns
            while occursin(old_pat, contents)
                contents = replace(contents, old_pat => new_pat)
            end
        end
        open("Dockerfile.2025", "w") do io
            print(io, contents)
        end
    end
end