Validate scope origin does not contain a path

This CL adds a validation to the `Session::CreateIfValid` method to
ensure that the scope origin does not contain a path (since it is an
origin, not a URL). Gated by `kDeviceBoundSessionsOriginTrialFeedback`
feature flag.

Fixed: 436634293
Change-Id: I1e91bd01e877fdbfa71161339d6e2edc17ac0af3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6840635
Reviewed-by: Daniel Rubery <drubery@chromium.org>
Commit-Queue: thefrog <thefrog@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1500261}