Add .NET Experimental Internal channel (#15512)

Co-authored-by: Ricardo Arenas <[email protected]>

Author: mmitche

src/Microsoft.DotNet.Build.Tasks.Feed/src/model/PublishingConstants.cs

@@ -76,6 +76,8 @@ public enum BuildQuality
 
         private const string FeedDotNetExperimental = "https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-experimental/nuget/v3/index.json";
 
+        private const string FeedDotNetExperimentalInternal = "https://pkgs.dev.azure.com/dnceng/internal/_packaging/dotnet-experimental-internal/nuget/v3/index.json";
+
         public const string FeedDotNetEng = "https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json";
 
         private const string FeedDotNetTools = "https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json";
@@ -259,6 +261,14 @@ public enum BuildQuality
             (TargetFeedContentType.Checksum, FeedStagingForChecksums),
         };
 
+        private static TargetFeedSpecification[] DotNetExperimentalInternalFeeds =
+        {
+            (TargetFeedContentType.Package, FeedDotNetExperimentalInternal, AssetSelection.ShippingOnly),
+            (TargetFeedContentType.Package, FeedDotNetExperimentalInternal, AssetSelection.NonShippingOnly),
+            (InstallersAndSymbols, FeedStagingInternalForInstallers),
+            (TargetFeedContentType.Checksum, FeedStagingInternalForChecksums),
+        };
+
         private static TargetFeedSpecification[] DotNetLibrariesFeeds =
         {
             (TargetFeedContentType.Package, FeedDotNetLibrariesShipping, AssetSelection.ShippingOnly),
@@ -1076,6 +1086,18 @@ public enum BuildQuality
                 symbolTargetType: SymbolPublishVisibility.Public,
                 flatten: false),
 
+            // .NET Experimental Internal,
+            new TargetChannelConfig(
+                id: 6820,
+                isInternal: true,
+                publishingInfraVersion: PublishingInfraVersion.Latest,
+                akaMSChannelNames: [],
+                akaMSCreateLinkPatterns: DefaultAkaMSCreateLinkPatterns,
+                akaMSDoNotCreateLinkPatterns: DefaultAkaMSDoNotCreateLinkPatterns,
+                targetFeeds: DotNetExperimentalInternalFeeds,
+                symbolTargetType: SymbolPublishVisibility.Internal,
+                flatten: false),
+
             // .NET Core Tooling Dev,
             new TargetChannelConfig(
                 id: 548,