Section outlet doesn't update when section content is rendered with streaming rendering

[danroth27]

Repro steps:

• Install .NET 8 RC1
• Create a Blazor Web App
• In MainLayout.razor add a SectionOutlet in the top row:

<div class="top-row px-4">
    <SectionOutlet SectionName="top-row" />
    <a href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
</div>

• In Weather.razor add a SectionContent:

<SectionContent SectionName="top-row">
    @forecasts?[0].Summary
</SectionContent>

• Run the app and browse to the weather page

Expected result: The weather forecast summary for the next day renders in the top row.
Actual result: The top row is empty.
Workaround: Disable streaming rendering on the weather page.

[SteveSandersonMS]

Thanks for filing this. We did intend to support this, and have a test implying that we do support it, but the solution we had (and what the test covered) was only if the streaming content came from a child component and wasn't going directly into the SectionContent.

I've implemented a fix at #50843