[FedCM] Send SameSite=Lax cookies, in addition to None
See discussion in w3c-fedid/FedCM#587
This is behind the FedCmSameSiteLax flag for now.
Bug: 350944661
Change-Id: I3e5fe99b98560f680217cd3326ff66d290a5290f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5675433
Reviewed-by: Yi Gu yigu@chromium.org
Commit-Queue: Christian Biesinger cbiesinger@chromium.org
Reviewed-by: Charlie Reis creis@chromium.org
Cr-Commit-Position: refs/heads/main@{#1325570}