Add IPAddress.IsValid

[MihaZupan]

Closes #111282

namespace System.Net;

public partial class IPAddress
{
+   public static bool IsValid(ReadOnlySpan<char> ipSpan);
+   public static bool IsValidUtf8(ReadOnlySpan<byte> utf8Text);
}

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[stephentoub]

What address does IPv4AddressHelper.Invalid represent?

[MihaZupan]

It's a -1 sentinel value

[MihaZupan]

/ba-g build failure is dotnet/dnceng#3008