[FedCM] Code changes to enable the origin trial for bundle 6

This is using "FedCmContinueOnBundle" as the origin trial name.

Bug: 40262526
Change-Id: I56a2935749fef2c2c99a0d1a2baefbf75c00f9ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5453246
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Nicolás Peña <npm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1288368}

credential-management/support/set_cookie.headers

@@ -1,3 +1,3 @@
 Content-Type: text/html
-Set-Cookie: cookie=1; SameSite=None; Secure
-Set-Cookie: same_site_strict=1; SameSite=Strict; Secure
+Set-Cookie: cookie=1; SameSite=None; Secure; Path=/
+Set-Cookie: same_site_strict=1; SameSite=Strict; Secure; Path=/