Stop copying content stream in .NET MAUI Blazor Windows

Fixes: #9206

microsoft/CsWinRT#670 and https://task.ms/31565319 have been marked as resolved. This PR removes the existing logic which copies the content into a memory stream, and replaces it with a call to `AsRandomAccessStream()` (`IRandomAccessStream` is still required per the `CoreWebView2` API).

I tried out CSS hot reload with this change and things are working as expected. Not sure if there's a particular behavior/technique we can use to verify the validity of this change. Spoke with @Eilon regarding this, and per his recollection things were immediately hanging, and that's why this change was necessitated.

src/BlazorWebView/src/Maui/Windows/WinUIWebViewManager.cs

@@ -83,15 +83,8 @@ protected override async Task HandleWebResourceRequest(CoreWebView2WebResourceRe
  if (TryGetResponseContent(requestUri, allowFallbackOnHostPage, out var statusCode, out var statusMessage, out var content, out var headers)
  && statusCode != 404)
  {
- // NOTE: This is stream copying is to work around a hanging bug in WinRT with managed streams.
- // See issue https://github.com/microsoft/CsWinRT/issues/670
- var memStream = new MemoryStream();
- content.CopyTo(memStream);
- var ms = new InMemoryRandomAccessStream();
- await ms.WriteAsync(memStream.GetWindowsRuntimeBuffer());
-
  var headerString = GetHeaderString(headers);
- eventArgs.Response = _coreWebView2Environment!.CreateWebResourceResponse(ms, statusCode, statusMessage, headerString);
+ eventArgs.Response = _coreWebView2Environment!.CreateWebResourceResponse(content.AsRandomAccessStream(), statusCode, statusMessage, headerString);
  }
  else if (new Uri(requestUri) is Uri uri && AppOriginUri.IsBaseOf(uri))
  {