Use new MemoryExtensions.Count and Json.WriteRawValue methods (#46332)

Author: BrennanConroy

src/Identity/Extensions.Stores/src/UserStoreBase.cs

@@ -920,6 +920,9 @@ public virtual async Task<int> CountCodesAsync(TUser user, CancellationToken can
         var mergedCodes = await GetTokenAsync(user, InternalLoginProvider, RecoveryCodeTokenName, cancellationToken).ConfigureAwait(false) ?? "";
         if (mergedCodes.Length > 0)
         {
+#if NET8_0_OR_GREATER
+            return mergedCodes.AsSpan().Count(';') + 1;
+#else
             // non-allocating version of mergedCodes.Split(';').Length
             var count = 1;
             var index = 0;
@@ -934,6 +937,7 @@ public virtual async Task<int> CountCodesAsync(TUser user, CancellationToken can
                 index = semiColonIndex + 1;
             }
             return count;
+#endif
         }
         return 0;
     }

src/SignalR/common/Protocols.Json/src/Protocol/JsonHubProtocol.cs

@@ -588,15 +588,7 @@ private void WriteCompletionMessage(CompletionMessage message, Utf8JsonWriter wr
             {
                 if (message.Result is RawResult result)
                 {
-                    if (result.RawSerializedData.IsSingleSegment)
-                    {
-                        writer.WriteRawValue(result.RawSerializedData.First.Span, skipInputValidation: true);
-                    }
-                    else
-                    {
-                        // https://github.com/dotnet/runtime/issues/68223
-                        writer.WriteRawValue(result.RawSerializedData.ToArray(), skipInputValidation: true);
-                    }
+                    writer.WriteRawValue(result.RawSerializedData, skipInputValidation: true);
                 }
                 else
                 {