Relax address-family check in DnsGetHostEntry_LocalhostSubdomain_RespectsAddressFamily on Android/AppleMobile

[Copilot]

On android-arm64, DnsGetHostEntry_LocalhostSubdomain_RespectsAddressFamily(InterNetwork) flakes because the Android OS resolver returns link-local IPv6 entries (e.g. fe80::…%47) alongside the requested IPv4 results for test.localhost, so Assert.All over AddressList fails on the wrong-family entries.

Changes:

• In src/libraries/System.Net.NameResolution/tests/FunctionalTests/GetHostEntryTest.cs, on Android and Apple mobile, require only that the requested family is represented (Assert.Contains) and skip the per-address Assert.All check. Strict validation is preserved on all other platforms.
• Mirrors the existing Android/AppleMobile relaxation pattern used by DnsGetHostEntry_LocalhostAndSubdomain_BothReturnLoopback in the same file.
• Factored the sync/async assertions into a local VerifyAddressFamily helper to avoid duplication.

bool strictAddressFamily = !PlatformDetection.IsAppleMobile && !PlatformDetection.IsAndroid;

IPHostEntry entry = Dns.GetHostEntry(hostName, addressFamily);
VerifyAddressFamily(entry, addressFamily, strictAddressFamily);

entry = await Dns.GetHostEntryAsync(hostName, addressFamily);
VerifyAddressFamily(entry, addressFamily, strictAddressFamily);

static void VerifyAddressFamily(IPHostEntry entry, AddressFamily addressFamily, bool strictAddressFamily)
{
    Assert.Contains(entry.AddressList, addr => addr.AddressFamily == addressFamily);
    if (strictAddressFamily)
    {
        Assert.All(entry.AddressList, addr => Assert.Equal(addressFamily, addr.AddressFamily));
    }
}

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