Address outstanding issues with System.Net MatchingRefApiCompatBaselines (#43230)

Author: stephentoub

src/libraries/Common/src/System/Net/Sockets/ProtocolFamily.cs

@@ -3,12 +3,15 @@
 
 #if SYSTEM_NET_SOCKETS_DLL
 namespace System.Net.Sockets
+{
+    public
 #else
 using System.Net.Sockets;
 namespace System.Net.Internals
-#endif
 {
-    public enum ProtocolFamily
+    internal
+#endif
+    enum ProtocolFamily
     {
         Unknown = AddressFamily.Unknown,
         Unspecified = AddressFamily.Unspecified,

src/libraries/Common/src/System/Net/Sockets/ProtocolType.cs

@@ -3,12 +3,15 @@
 
 #if SYSTEM_NET_SOCKETS_DLL
 namespace System.Net.Sockets
+{
+    public
 #else
 namespace System.Net.Internals
-#endif
 {
+    internal
+#endif
     // Specifies the protocols that the Socket class supports.
-    public enum ProtocolType
+    enum ProtocolType
     {
         IP = 0, // dummy for IP
 

src/libraries/System.Net.NameResolution/src/MatchingRefApiCompatBaseline.txt

@@ -1,3 +1,4 @@
+# Public in the implementation to maintain binary serialization compatibility as the System shim needs to have access to type-forward to these
 Compat issues with assembly System.Net.Primitives:
 TypesMustExist : Type 'System.Net.CookieVariant' does not exist in the reference but it does exist in the implementation.
 TypesMustExist : Type 'System.Net.PathList' does not exist in the reference but it does exist in the implementation.

src/libraries/System.Net.Primitives/src/MatchingRefApiCompatBaseline.txt

@@ -160,11 +160,6 @@ public bool AreParametersAcceptableForCaching()
         private const string ContinueHeader = "100-continue";
         private const string ChunkedHeader = "chunked";
 
-        [Obsolete(Obsoletions.WebRequestMessage, DiagnosticId = Obsoletions.WebRequestDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
-        public HttpWebRequest()
-        {
-        }
-
         [Obsolete(Obsoletions.WebRequestMessage, DiagnosticId = Obsoletions.WebRequestDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         protected HttpWebRequest(SerializationInfo serializationInfo, StreamingContext streamingContext) : base(serializationInfo, streamingContext)
         {