Fixes dotnet#5105

Add support for HttpRequestMessage objects containing StreamContent to
the AddStandardHedgingHandler() resilience API.

This change does not update any public API contracts. It updates
internal and private API contracts only.

This is a small commit that is part of a larger PR. See the PR and
its corresponding initial commit for the full set of changes.

test/Libraries/Microsoft.Extensions.Http.Resilience.Tests/Resilience/RequestMessageSnapshotTests.cs

@@ -10,6 +10,7 @@
 using System.Threading.Tasks;
 using FluentAssertions;
 using Microsoft.Extensions.Http.Resilience.Internal;
+using Microsoft.Extensions.ObjectPool;
 using Xunit;
 
 namespace Microsoft.Extensions.Http.Resilience.Test.Resilience;
@@ -108,6 +109,18 @@ public async Task CreateSnapshotAsync_OriginalMessageChanged_SnapshotReturnsOrig
 #endif
     }
 
+    [Fact]
+    public async Task CreateRequestMessageAsync_SnapshotIsReset_ThrowsException()
+    {
+        _requestMessage!.Method = HttpMethod.Get;
+        Assert.Null(_requestMessage.Content);
+        AddRequestHeaders(_requestMessage);
+        AddRequestOptions(_requestMessage);
+        using RequestMessageSnapshot snapshot = await RequestMessageSnapshot.CreateAsync(_requestMessage).ConfigureAwait(false);
+        ((IResettable)snapshot).TryReset();
+        _ = await Assert.ThrowsAsync<InvalidOperationException>(snapshot.CreateRequestMessageAsync);
+    }
+
     public void Dispose()
     {
         Dispose(true);