Add partitioned to cookie for SignalR browser testing (#57997)

* Add partitioned to cookie for SignalR browser testing

Looks like Chromium (not chrome) headless now requires 'partitioned' on the cookie when using `Secure` and `Same-Site=None`

* Apply suggestions from code review

Co-authored-by: Andrew Casey <amcasey@users.noreply.github.com>

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Co-authored-by: Andrew Casey <amcasey@users.noreply.github.com>

src/SignalR/clients/ts/FunctionalTests/Startup.cs

@@ -184,9 +184,11 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<
                 {
                     cookieOptions.SameSite = Microsoft.AspNetCore.Http.SameSiteMode.None;
                     cookieOptions.Secure = true;
+                    cookieOptions.Extensions.Add("partitioned"); // Required by Chromium
 
                     expiredCookieOptions.SameSite = Microsoft.AspNetCore.Http.SameSiteMode.None;
                     expiredCookieOptions.Secure = true;
+                    expiredCookieOptions.Extensions.Add("partitioned"); // Required by Chromium
                 }
                 context.Response.Cookies.Append("testCookie", "testValue", cookieOptions);
                 context.Response.Cookies.Append("testCookie2", "testValue2", cookieOptions);